Leo Beranek

Announcer:

Well, thank you all for coming. We will now begin an afternoon with Leo Beranek. Our moderator today is Jack Purcell; an old friend of Leo’s who’s graciously agreed to serve as sort of the interlocutor. Those of you who have come to the afternoon sessions, however, know that the whole idea of this is a conversation between Leo and everybody here. Jack does his best job if he doesn’t do anything at all. So, feel free at any time to ask questions and become involved, because this is, ideally, just a large living room conversation among friends.

Purcell:

Well before I do nothing at all, I’d probably best introduce myself. My name is Jack Purcell. I first met Leo Beranek in 1950, December of 1950. I graduated from Catholic University of American in Washington, D.C. and I had taken my bachelor’s degree in architecture. I had acquired a scholarship at MIT, and when I went there I took some courses in architectural acoustics and I met Leo Beranek. That was 1950. One of partners, Doc Newman, invited me to attend a session one afternoon at their offices because they were doing a project in New York and had some questions concerning some architectural plans. I went over and looked at it, and it was the United Nations General Assembly. That was the day I really met Leo Beranek. Leo, at that time, was designing the audio system for the General Assembly building, which was a very, very difficult, very interesting and very complex project. As we were discussing a little bit earlier, the consultant on the project (who was from Europe) took umbrage at Leo’s design, said it would never work and resigned from the project, indignant of the whole process. Leo kept his cool, they installed the system, it worked and was a very great success.

Beranek:

He wasn’t a consultant, he was the head of telecommunications for the entire United Nations, and he quit his job over this. He didn’t want his name blackened with this mess. But, it turned out not to be a mess.

Purcell:

Well, at any rate, that was my first meeting with Leo and I must say that, for myself, before I get into Leo, the initial meetings I had with Leo and the gentlemanly attitude of this incredible person so influenced me that I left architecture, and never went back to it. Ostensibly, I shifted into the field of acoustics and from Leo’s inspiration I saw what acoustics could do for architecture. I am now involved pretty much in architectural acoustics, voice control and related facilities. So, my field of expertise primarily is architectural acoustics. Now, I want to get into Leo Beranek, because that’s what we’re here to talk about, talk with and communicate. Leo’s a graduate of … I’m going to have to do a little reading because in forty years you forget some of these things. But Leo was born in 1914 in Iowa. Leo received his B.A. degree from Cornell College in Iowa, majoring in physics and mathematics. He received both his Master of Science and Doctor of Science from Harvard University in 1937 and 1940 respectively, and received honorary doctorates from Worcester Polytechnic Institute, Northeastern University, Cornell College, Suffolk University, and Emerson College. So, he’s a doctor many times over, much to his credit, and is certainly most deserving of it.

Leo began as an instructor in communication physics, and directed electro-acoustics and systems research laboratories during World War II, for which he received the Presidential Certificate of Merit in 1948. Following that, immediately after the war, he joined the MIT faculty as associate professor of communication engineering in 1947, a position which he held until 1958. Leo is with us today to reminisce and talk about things that interest you and me and himself. We’ll keep it an informal session, and I think that … Leo, I’d like to go back to the early days when we first started Bolt, Beranek and Newman (we first of all, it wasn’t we-it was Bolt, Beranek, Newman, Labate, Baruch and Purcell, I was the sixth member of the firm, although it went on to 2000 people eventually). The first of Leo’s projects that I was aware of was the Cleveland wind tunnel, which was a fascinating project. Very briefly, the Cleveland wind tunnel was the largest wind tunnel for engine tests ever constructed at the time, and in order to function it had to operate only at nighttime, because the amount of electrical power that it took to run that facility was so great they had to shut down at least two-thirds of the city power in the city of Cleveland in order to run the facility. Of course, that created a very interesting problem: Noise, and things which I will leave Leo to talk about, because he pioneered some very interesting concepts as a result of that.

Beranek:

Well, let me go back a little further. Because you here today are in audio, I want to explain how I got into audio to start with. My interest in audio began in Cornell College. The speech department decided that the speech students ought to be recorded. The recordings were home recording quality, necessary, because we couldn’t record in wax, which was how all the commercial recordings were done at that time. The recordings were made on aluminum disks using a large, heavy transducer with a needle on the end that would emboss a wiggly sound groove on the aluminum. It was played back with fiber needles, which had to be kept sharp, and the pickup moved inside out because that was the only way one could keep the tone quality from deteriorating as the needle wore down. The tone was better on the outside grooves, compared to that on the inside.

So, I made recordings and would play them back for the students. The students would get the recording to take home, and it probably cost them $1.00 a piece in those days. I had to build a little studio to do the recording in, because the room they gave me was too reverberant. That got me interested in acoustics, interested in recording and sound. When I decided to go on to graduate school, I decided I would go into radio (of course, they had no television in those days). We didn’t speak of electronics yet, it was called radio. The story of how I got from Cornell College to Harvard is one I’d like to relate. In my junior year I had decided I wanted to go on to graduate school (Cornell had just had an undergraduate, liberal arts curriculum). I thought of going to one of the schools around Iowa, like the University of Illinois or the University of Minnesota or the University of Kansas, Missouri or somewhere — the University of Iowa, even — and I decided than I would apply to all of them. I think, in those days, the time to do it was right after you got back to school from your summer vacation (this would be my senior year). Decisions as to acceptances were made along about May 1. In those days there was no trouble being accepted by any school, even Harvard, provided one had decent grades and the money to pay the tuition. Money was all that counted.

We were in the midst of the Great Depression, (this was ‘35 I’m talking about). I had no money because the family had lost everything. The banks were going bust, everything went to hell for my parents and I had to have financial help or I couldn’t go. So, application to all these schools was not for admission, it was for a scholarship, because I had good enough grades to pass any of the schools’ requirements. Well, this was in August, in 1935. I’m walking down Main Street in Mt. Vernon, Iowa, and the Lincoln Highway, which was then the principal East-West highway, Route #30, starting in Washington, D.C. and ending in San Francisco. It was hot as hell — the temperature must have been 100 degrees in the shade. As I was walking along the street I came on a Cadillac that had a flat tire. There was a nicely, dressed fifty year old man standing alongside of it. He looked absolutely miserable. I was in the equivalent of dungarees and said, “Could I help you with your tire?” He thought that was a good idea, so I did the dirty work, he kept himself clean and told me where things were. I changed the tire. Of course, we began to talk. He said, “What do you do?” I said, “Well, I go to the college here called Cornell.” Yes, he’d heard about it, we talked back and forth, he asked, “What are you interested in?” I said math and physics, “I want to go into radio.” He said, “That’s my field too.” I indicated I wanted to go the graduate school. So, then he talked a little more (What are your plans?”) I said, “Well, I don’t know. I’ve got to have full scholarship help and maybe some supplementary help too, I have no money.” He listened and didn’t say much. I said, “By the way, what’s your name?” He said his name was Glenn Browning. I froze and said “You’re Glenn Browning? I read a paper you published in the IRE this morning.” (We called the IEEE the IRE in those days, meaning the Radio Engineers.) Instantly I had a friend. I had read a paper of his. He asked, “Where are you going to go graduate school?” I told him about these applications. He said, “Well, why don’t you go to Harvard?” I said, “That’s a rich man’s school, I never thought of it.” He said, “Well, they’ve got more money for scholarships that anyplace out here, and I can do you some good there. I’ll tell you exactly who to write to get the application forms. Use me as a reference. Well, I did all that. Then came spring and I was turned down by all these schools in the Middle West, every one. “A fine recommendation, but we don’t have enough money for all the requests for scholarships, we’re sorry.” Harvard came through with the full works. So, I went to Harvard.

Purcell:

The luck of the draw.

Beranek:

The luck of the draw. Changing the tire, and having read his paper that morning! So, read every paper you can.

Purcell:

Very interesting, Leo, very interesting. Leo, what research did you do in developing the first “anechoic: chamber?”

Beranek:

Well, again, first I’ll tell a sequence of things. I got my doctorate in June 1940; nothing special about my getting it. I went into acoustics, because Harvard had a tradition in that field. Wallace Clement Sabine had developed the “Sabine” reverberation equation. Professor Hunt was the senior acoustics man there, the same as Knudsen was here at UCLA. My doctoral dissertation was on measurement of acoustic impedance, which had not been done seriously before. In 1940, the U.S. government started in a big way helping the British in the war effort. The Radiation Laboratory was formed at MIT in the summer of 1940. The second laboratory to be formed was the one that I directed called Research on Sound Control (the name they gave it), which started out as an effort to quiet noise in airplanes. Our principal long time contribution was the development of an acoustical material, light in weight. The product was then manufactured by the Fiberglass Company. It is very fine fiber that is used as aircraft lining. It has a maximum area of surface per fiber compared to its weight, which means the fiber diameter has got to be very small, i.e., to get a lot of surface area for a given weight. Research on Sound Control then turned into the Electro-Acoustic Laboratory. Having developed the acoustical material, our next project was to improve voice communications in aircraft. Pilots and crew were having trouble at high altitudes, because the microphones went bad, the earphones went bad, and we didn’t know what happened to the voice and the ear. We started research on voice communication at high altitudes. At the Harvard public School of Health they had a chamber in which they could reduce the pressure, equivalent to going up to 50,000 feet (of course you have to use oxygen masks) We learned that the hearing did not deteriorate with altitude, but that the voice weakened as the density of the air decreased. Also we had to find new microphones and new earphones and get them into the services in a hurry, because they needed them. We also developed doughnut cushions (we called them) that went around inside the helmets around the ears to keep the noise out. The earphones, of course were mounted on the outside edge of the doughnut.

Purcell:

These were circumoral?

Beranek:

Yes, against the head, around the outer ear. The improvement in noise reduction inside the helmets was considerable. The earphones, microphones and cushions were so important that the government took over, on our recommendation, the big Hawthorne plant of AT&T. next to Chicago, and ordered it to make new microphones and earphones as fast as possible. They were needed in all airplanes for the Army, the Navy, the Air Force and the British …The Royal Air Force.

Purcell:

This was a manufacturing plant in Hawthorne, Illinois?

Beranek:

Yes, operated by Western Electric, then a division of AT&T. It was their big plant. The equipment was produced so fast it was unbelievable, because the need was so great. When we got that job done, the next thing they asked me to do (December 1943) was to start a laboratory called the Systems Research Laboratory. Its task was to speed things up in the combat information centers on ships so that they could do something about the kamikaze airplanes that were coming in, not being detected, and ramming into the ships and blowing them up. So much of the Navy superstructure on U.S. war ships was damaged that there was no chance of mounting an invasion of Japan soon. We were asked, quick, “solve the problem.” We quickly built a ship on land at the mouth of Naragannset Bay. There’s an island there on which the city of Jamestown, Rhode Island is located. The tip of the Island is called Beavertail Point. We built this “ship” on land, with radars and all. Then airplanes from the Quonset Air Force Base, would raid our “ship.” Our radars were supposed to work so fast that you could detect aircraft coming and give commands to the guns to turn that way and shoot. Our laboratory at first couldn’t get any modern radar equipment because we were not at sea. The Navy rules were that nobody on land could have modern radar equipment; new stuff had to go to the fleet. So, the U.S. Navy commissioned my laboratory as a ship! I was “captain” of the U.S.S. Beavertail! All the radar equipment was “U.S.S. Beavertail.” By the winter 1944-45 we had figured out how to speed things up. In August 1945 the U.S. decided to drop the atomic bomb, the war was over and we were put out of business and closed down. It was an interesting period.

Purcell:

Following up on your initial research into the effects of altitude on hearing and speech, why was the speech affected, or why was the production of speech affected?

Beranek:

Because the density of air went down.

Purcell:

Just the density of air?

Beranek:

Yes.

Purcell:

And the human vocal track…

Beranek:

Wasn’t able to push around as much air when the vocal cords vibrated that meant you had a weaker signal.

Purcell:

But altitude didn’t affect hearing?

Beranek:

Hearing was not affected. You see, the change in pressure was balanced out by the eustachian tube.

Purcell:

How did you modify the microphones?

Purcell:

Was that how the hollow throat mike came to be?

Beranek:

No, the throat mike was the worst. We make a campaign against throat mikes. What we got Western Electric to do was to build a wide frequency range mike to put in the oxygen mask in front of the eyes. It did not have a flat response, because when you put it into the oxygen mask, the oxygen mask boosts the low frequencies. The response had to drop off at six decibels per octave, below roughly 3,000 hertz. Then in the mask you’d come up with a pretty flat frequency response, band response, band response. The microphones before that time were all resonant at around 1,000 hertz, and were terrible. The earphones were the same thing. They were resonant. We got W.E. to bring in the damped diaphragm, the damping mechanism from behind, which also had to be adjusted in both resistance and size of cavities so it would stay flat at high altitude. The damping must not go bad at high altitude, and those were the improvements. And the cushions.

Purcell:

Now, this equipment worked at low altitudes as well…

Beranek:

Yes.

Purcell:

How much electro-acoustics was going on before the war, when you were getting your graduate degree?

Beranek:

Well, much of the basic work that was going on before the war was being done at Bell Labs and ERPI Electrical Research Products Inc., a subsidiary of AT&T. They and REC were putting out loudspeakers microphones and so on. The driving force before the war was talking movies. That started coming in, I would say, about 1930, the war effort began in 1940 (we entered the war in 1941.) So, most of the work prior to 1940 was done in connection with the movie theaters.

Purcell:

What was Harvard doing in electro-acoustics? Anything to speak of…?

Beranek:

There were two interesting things going on in that period at Harvard. One was architectural acoustics, trying to study how sound was propagated in rooms. We were examining the practical aspects of normal mode theory in room acoustics (nobody else had done that before MIT and Harvard). But, the interesting thing I was involved in was working as research assistant to Professor F.V. Hunt during the period that he developed the first light-weight phonograph pick-up. Go back one bit farther. Harvard was 300 years old in 1936, so they recorded the entire tercentenary celebration on acetate disks. The recording needle would cut out thread of the acetate to make a sound track. So they recorded the entire, three-day celebration of their 300th anniversary. President Roosevelt came and spoke and as did many dignitaries from around the world. I landed at Harvard in September 1936, and this recording started practically at the time I arrived. Well, now the question was, how are you going to play these records back? If you played them back with any conventional playback head that weighed an ounce or so, you would wreck those disks. So, Hunt decided the thing to do was to develop a lightweight pickup. He developed the first one-grain pickup that then led to the 33 1/3 disk, or the 33s and 45s. It was on the front cover of Electronics Magazine about 1938 or ‘39.

Purcell:

Was that a crystal pickup?

Beranek:

No, it was a moving coil.

Purcell:

Moving coil. Aha.

Beranek:

He got a patent on that particular design, but Fairchild came out with a different moving coil pickup. He couldn’t patent the concept of the moving coil, because that had been around for a long time; he could only patent his particular configuration. Fairchild, instead of licensing under his patent, developed their own version and they took over the light-weight pickup market.

Purcell:

That was a beautiful pickup in its day, a good pickup.

Beranek:

So, I was in on the birth, you might say, of the 33-45 records, working for Hunt as his laboratory assistant.

Purcell:

Was he your thesis…

Beranek:

Hunt was my thesis advisor.

Purcell:

Did you collaborate at all during the war with the arch rival/enemy camp at MIT, specifically Professor Morse?

Beranek:

Oh, yes. Well, Morse and Hunt had been great friends. They lived in apartments above each other in the same building. But, among the students there was vigorous rivalry. We were trying to outsmart MIT’s graduate students and vice versa. As a result, acoustics of rooms moved rapidly in that period, because of the intense competition. But, much later (1947) Morse was the one who got me to join MIT’s faculty.

Purcell:

What was your thesis topic?

Beranek:

It was on measurement of the acoustic impedance of acoustical materials.

Purcell:

Covering a variety of materials?

Beranek:

Yes, I first published impedance data on acoustical materials.

Purcell:

Tube measurement as well, or…?

Beranek:

These measurements were done in a 3-inch diameter tube. Morse used my data as a basis for a theory of predicting the acoustical behavior of porous materials.

Purcell:

Is that his “Smith Chart” application?

Beranek:

That’s right. I included his Smith Chart in my 1949 “Acoustic Measurements” book.

Purcell:

Yes, but the Smith Chart originally was generated from electrical ratios…

Beranek:

That’s exactly right.

Purcell:

Dr. Hunt, who in his book Electric Acoustics talks about many things. Can you maybe give us some background on some of the things you may have contributed to, in that book?

Beranek:

Well, I didn’t contribute much to his book. Hunt’s work dealt principally with recording. He did the pickup, and I was his lab assistant, but really everything he did was his idea. I didn’t contribute to the basic concepts; I was too fresh there for that. Then followed his research on the distortion you get on playback due to a finite-size needle going down the groove, called “tracing distortion.” Hunt, and a colleague, Jack Pierce, who was a senior research assistant there, worked on that. What I did as his assistant, which was not very interesting, was to develop the very best high quality playback system, at least that we had at Harvard. I bought and designed the best driving units made by Jensen for the woofers, and had our shops build a big folded horn arrangement out of wood, with two Jensen twelve-inch drivers. I forget what we were using for high frequency drivers. Probably, Jensen had high frequency units then. I don’t remember. Then, we got acquainted, of course, with the ERPI people, who developed the first multi-cellular horns. We soon had multi-cellular horns for the high frequencies. In regard to his book, he did all the writing himself, at home. I didn’t help with the book.

Purcell:

He was also fascinated with electrostatics, at least later on, in the late ‘40s and ‘50s…

Beranek:

Yes, Paul Jensen, his doctoral student, after I left MIT in 1947, started his work right after that.

Purcell:

There is also a lot of impedance data in that book, about loudspeaker mechanical impedance block, motion impedance. Is that related at all to your mechanical impedance work, that you did earlier?

Beranek:

No, I didn’t really get into trying to do something about loudspeaker impedance until I got to MIT. MIT’s first instruction to me was to develop a course in acoustics. I landed on my feet there in February and I started teaching the new course in February, so I had to keep one page ahead of the students; I had no chance to develop the course in advance. But, I had thought seriously about this question of electro-acoustic analogues, analogous, circuits which then led to my book Acoustics, which, incidentally, was reprinted two years ago by the Acoustical Society of America. I put into one circuit diagram the electrical, the mechanical and the acoustical elements so you could read right through them. Whereas, if you look into Harry Olsen’s books, he always had the electrical side separated from the mechanical and acoustical side and said you should join them together by an equation. But, to see the whole operation all in one circuit was a great advantage. You could see what “wiggling” an element did, as you always do in electrical work, and that’s what led to the development of the little loudspeakers. Because three of my students were E. Vilcher, Jordan Baruch, Henry Lang [who came out the first of the small speakers called the Baruch-Lang loudspeakers and KLH Henry Kloss. These fellows developed small speakers, starting from the circuit theory that I was teaching. I didn’t develop the speakers, they did.

Purcell:

One other thing I’d like to ask if I may: You started your studies in acoustics during the late ‘30s. Prior to that there was Dr. Miller’s work at Case Western, where he had started off with some of his work and had actually inspired Dr. Morse. There was also Dr. Knudsen, out here.

Beranek:

Yes.

Purcell:

Did they influence you, or…?

Beranek:

Of course they were in the literature that I studied. Knudsen had many students and they all did different things, but his big, personal contribution was working with a fellow named Kneser on the absorption of sound while traveling in air, a very important step forward. Then he developed architectural acoustics as a practice, and did a lot of work in building acoustics himself, in working with Bob Leonard and Leo Delsasso. Those were his two principal helpers at that time. Those three were the power on the West Coast. Then, in the Middle West it was Floyd Watson, at the University of Illinois, who was the leader in architectural acoustics. Miller was fairly old. He practically died at about the time I got into acoustics, so I never really got to know him. I met him once; he died almost the next year.

Purcell:

Was your friend with the tire problem Browning of Browning Laboratories?

Beranek:

Browning Laboratories, that’s the fellow. Yes.

Purcell:

Where were their offices?

Beranek:

In Winchester, Massachusetts.

Purcell:

That’s right, it was Massachusetts. I wasn’t sure. I’m from the East too. Washington, D.C.

Beranek:

Browning was my God, you see.

Purcell:

Friend with the tire?

Beranek:

My tire story.

Purcell:

When you got to MIT, Leo, and then I guess you and Dick Bolt started getting together.

Beranek:

But, first you asked something about the anechoic chamber.

Purcell:

Yes, I did. I was interested in that.

Beranek:

Well, that research was done at Harvard, as part of my war work. One of the requests that came through from the ground forces was they wanted to develop loudspeakers they could use on beach landings, to give instructions to troops. They wanted big speakers that would make a lot of racket, and they wanted them to be as efficient as possible and as lightweight as possible. So, they put out a request for designs to various companies, including Jensen and ERPI and whoever else was in business –- REC — and they wanted some place to test these. Well, if you test them outdoors you’ll find that you don’t have any friends among your neighbors. So, we had to develop an enclosure. I went to the National Defense Research Committee and asked them for money to run a research project and to build this building. Everything had to move fast in those days because there was a war on. First I got a senior student (his name was Harvey Sleeper), at Harvard to take data for me. He was in physics. We took data on different shapes of wedges and different lengths, etc., which led to our paper, on anechoic chambers (published after the war in 1946) decided that a wedge shape that was about three feet long with an 8” square base and stuffed with a certain kind of fiberglass, (certain size of fibers). Also behind the wedge we found you could improve it by having an air space. We decided to use that as a basis for building an anechoic chamber in 1943. So, we got enough money from the government, something like $350,000 to build a concrete building that was 50 ft. square inside (it wasn’t quite square; it was off a little. We didn’t want it absolutely square.) We lined it with seven railway carloads of fiberglass, made into these wedges. That was the first anechoic chamber to be built in this country, of any size. Bell Labs had a small one that they called a soundstage, made out of parallel layers of muslin stretched up. It was nowhere near as good.

Purcell:

Where was this facility built?

Beranek:

At Harvard, and it existed at Harvard until 25 years after the war was over. Harvard decided they weren’t going to carry on acoustics after Hund died, so the government said that within 25 years they would tear anything down they had put up during the war, free of charge to Harvard, and Harvard said to tear it down. So, there’s no anechoic chamber at Harvard today.

Purcell:

Did it have a steel, cable floor?

Beranek:

Yes.

Purcell:

What was the thickness of the poured concrete?

Beranek:

I don’t know, six inches or so.

Purcell:

Was that man “Sleeper” Milton B. “Sleeper” who started that magazine in Great Barrington, Massachusetts?

Beranek:

No, this “Sleeper” went to work at the NASA Kennedy Space Center and I guess he’s still there.

Purcell:

Where did the concept of the wedges come from? Were there radio anechoic chambers before that?

Beranek:

The wedge concept was mine. Erwin Meyer in Germany had developed a chamber using cones and it worked pretty well. My study showed that wedges were much better than cones.

Purcell:

Is that an outgrowth of your work on acoustic impedance; did that kind of follow?

Beranek:

Well, in the sense that the tests for the wedges used the same kind of equipment. I used an eight-inch-square tube for the test. Actually, there’s nothing I can see in the studies I made in the three-inch tube for my thesis that was directly applicable to these wedges. I had to start from nothing.

Purcell:

The analogy you made at the time was that it was, in effect, a type of transformer.

Beranek:

That’s right. In fact, a sound wave was lured into it in a sneaky manner. The wave would encounter little at the beginning of the wedge and then would gradually be absorbed as the wedge got larger. Finally it would be fully absorbed at the bottom.

Purcell:

So what year was the chamber built?

Beranek:

It was built in ‘43.

Purcell:

Do you know offhand, then, what year the chamber that is currently at Bell labs was built? Because I always thought that the current Bell Labs chamber was the first anechoic chamber.

Beranek:

It was built after the war. Now, let me be straight on this (we may both be telling the truth). Bell Labs intended to build a chamber before the war, and they put up a big cube building, with nothing in it. They left it empty until after the war. After the war, when they saw what I did, they hired Cyril Harris (he was at MIT at that time). His first project at Bell Labs was to line that big box that had been standing there empty. So, they used my designs in building that box, and Cyril Harris was in charge of it.

Purcell:

When was Olsen’s RCA chamber done?

Beranek:

Olsen’s RCA chamber was done almost at the same time as ours at Harvard, and the reason I know that is he was on the Acoustical Society program to tell about the RCA chamber as the same time that we’d finished our chamber. I had not gotten my paper, to throw a few slides on the show the Acoustical Society that we had one too, quite different in design.

Purcell:

When did you meet Mr. Newman and Dr. Bolt?

Beranek:

Bolt I met while I was doing my doctoral thesis. There was a meeting in 1939 of the Acoustical Society of America at Harvard. They only had one session (no parallel sessions) in those days, and it was held in the physics lecture room in the Jefferson Physical Laboratory. Bolt came East from California (he was then working with Knudsen), to go to this Acoustical Society meeting. So, the first time I saw him was when he walked into my research room at Harvard, introduced himself, and said he was going to the meetings (which started the following Monday, and this was like Friday or Saturday, I was at work, getting my paper ready; he had to come a greater distance.

Purcell:

He may have written it on the train.

Announcer:

He was studying with Dr. Knudsen?

Beranek:

That’s correct. Then he came back here, got his doctorate, actually out of Berkeley. His official doctorate was from Berkeley, but he did his research down at UCLA under Knudsen, because Berkeley didn’t have acoustical facilities.

Purcell:

Interestingly, he had done an architectural degree at Berkeley, prior to going into physics. When he came out of college and saw there was nothing to do in architecture, he went back into physics, and then went down to UCLA.

Purcell:

But he was a West Coast…

Purcell:

He was a West Coast product, yes. His parents lived in Berkeley.

Purcell:

Because, I always thought he was from the East Coast, based on that Review of Modern Physics he did in 1947.

Beranek:

He did that with Philip Morse. But, you see, after the war was over, he came East and got an assistant professorship under Phil Morse, and he came there I think in … the war was over in ‘45, as you remember, and he came almost right away. I don’t know if he came in the fall of ‘45 or the spring of ‘46. I came in the spring of ‘47 to MIT, and the two of us, then, built up the acoustics there.

Purcell:

Then, what year was the formation of Bolt, Beranek and Newman?

Beranek:

Well, that came about for two reasons. First, there was a bidding contest between Knudsen and Bolt over who was going to do the acoustics of the new UN headquarters in New York. Knudsen’s price came in higher because he had to travel across country, requiring increased time and transportation costs. Bolt, being on the East Coast, could underbid him, even though they were charging about the same amount per day and per hour. When the job came in, it turned out to be much bigger than anybody thought that, of course, the contract had to be renegotiated. Then Bolt decided he couldn’t do the thing alone, without help, and I was, of course, in the same lab with him. On the other hand, I had a problem too, because it turned out that the owner of most the New York movie theaters, particularly in Brooklyn and Manhattan wanted to redo and upgrade those theaters (television hadn’t hit yet). So, he started out with a contract to do 50 of them. We got two done by the time television hit New York, in 1948. So, my part in this wasn’t very important. So, Bolt and Beranek was formed in 1948. About the same time, in the late summer of ‘48, when we were joining together, we decided to hire somebody to help us. We hired Bob Newman first, to help us, so we could do both the UN and this movie theater job and could continue to teach.

Purcell:

And Bob Newman was a student?

Beranek:

He was a student, yes.

Purcell:

At MIT?

Beranek:

At MIT.

Purcell:

Interestingly enough, he had his degree in physics from the University of Texas, a master’s degree, and was taking an architectural degree at MIT. So, it was a good situation both for him and Dr. Bolt and you.

Beranek:

Newman ??? named a partner one year later… I mean, he came to work for us the first year, but we put him into the partnership a year later and changed the name to Bolt, Beranek & Newman. By that time he had his degree.

Purcell:

That was what year, ‘49?

Beranek:

Yes, the firm, with two names, started in November of ‘48. So, we just last November turned … how many years? Forty years old.

Purcell:

Back to the question of your work on acoustical impedance? Was this all a direct extension of the work that Bell Labs did in the early and Mid-‘20s, in their design of loudspeakers and recording heads, etc., the “orthoponic” phonograph? Or, was there ever a point at which people started going off in a different direction?

Beranek:

Well, you see, the Bell Labs work was all aimed toward theater acoustics — loudspeakers, and microphones and recording optically sound tracks of film. They did do some lining of rooms, some of the theaters, through the ERPI Company that Western Electric owned. My work, however, was on acoustical materials, basic studies of what went on inside of them, what made them work acoustically. I set out to get data on the impedance a number of materials both the real and imaginary parts of the ratio of pressure to particle velocity at their surfaces; then, from that, be able to study what was happening inside. I published my data first, then Morse put his mind to work, being good in theoretical physics, and developed the first theory of what went on inside these materials. When my second paper came out later some years later; I had a little different version of the theory of what went on inside the materials, and which became the basis for studying wrappings and acoustical blankets used in noise control.

Purcell:

Can you talk a little on the General Assembly system?

Beranek:

Oh, yes.

Purcell:

I remember a cellular horn on the podium?

Beranek:

That’s right. What happened there was, as we were saying before you came in, the shape of this General Assembly Hall was a big cone, and circular at the base it went up and then stopped half-way before the tips. They put a dome on top, so they had a circular room, circular sides going up with a circular dome on tip-a great acoustic nightmare, as you can imagine. So, we are given that assignment to make good on. Among other things, the hall was big enough that you just knew you had to have sound system, there was no way you could cover that big a hall with voice. To make the room work we put parallel vertical slats all around the inside.

Purcell:

That’s exactly when I joined the firm. We did the parallel slat thing, which became an acoustically transparent screen with a visually opaque surface, behind which there’s sound absorbing material to kill off room resonances.

Purcell:

This is 1948?

Purcell:

This was 1950. The plaster behind all the wooden slats is highly serrated, and there are random patches of acoustical, sound absorbing, sound reflecting materials, which totally diffused the sound. We knew that electrical acoustics was not going to function unless we did something with the acoustics of the space first. We used acoustics plaster on the dome, which was the best product we had in those days. It was a monolithic surfacing material. Of course, it’s verboten now because it’s full of asbestos. But, we had those materials to work within those conceptual designs, and at that point we got it up to speed, as far as the room acoustics were concerned, to the state-of-the-art (which, incidentally, has not changed a hell of a lot, I want to point out. I still employ the techniques successfully). Then, Leo got to work on the audio systems design, which I think is interesting.

Beranek:

We had, of course, two things to do. One was we had to put a loudspeaker at every desk, because they wanted to hear well. Also they wanted to plug in earphones and to listen to simultaneous translations — in French or Russian, or whatever, by turning the knob in connection with the earphones. The loudspeaker always had to be on the language being spoken at the podium. That was at every desk. We had a distributed loudspeaker system, with little speakers (4 inches on diameter) desks, so as the delegates wrote they could look into the loudspeakers, just above the surface of the desk that they were working on. They also wanted a general coverage loudspeaker that would cover all the seats or the audience, partly because they didn’t know whether these little speakers were going to work or not, and they wanted the sound to come out so everybody could hear the same thing. Remember, now, the wall had to be behind the podium slanting, because it was a cone, as I said and the podium had to be out in front, a distance of … what would you say?

Purcell:

Forty feet, probably.

Beranek:

Well, maybe it was 40 ft. in front of that big wall, always think of it as more like 25 ft., but maybe you’re right. The logical thing to do was hang a cluster of loudspeakers above the podium, which would give you good coverage without feedback. The architect worked hard on trying to figure out how to put an emblem up there, hanging above the podium, and put the speakers behind it. The architect finally said “No go.” This was Wallace K. Harris, of Harris & Abramovitz. “We’re just not going to have a pile of junk up there. It’s going to be put in the wall, behind the podium.” Of course, you’re up here at this podium, and whether it was 30 ft. or 40 ft. from where the loudspeakers were, you’re well ahead of the loudspeakers. God, the scary thing was to look around and see those speakers up there, just over one’s shoulder. They were, of course, behind an emblem and the emblem was made transparent enough so the sound could come out without hindrance. The opening was about six feet square. We put in a what-do-you-call-it…

Purcell:

There were about six multi-cellular horns in there…

Beranek:

Yes. What’s the company’s name…?

Purcell:

Was it ALTEC then?

Beranek:

ALTEC, yes. The ALTEC system was the one installed.

Purcell:

What about the time delay of the sound, having a speaker that far behind?

Beranek:

It certainly could have oscillated. We had no notch filters in those days, available, and it never even occurred to us to make any. If there had been a resonance anywhere in that system we would’ve been sunk.

Purcell:

You used an “omni-directional” microphone probably.

Beranek:

Yes. We used those little small ALTEC microphones that went down and kind of fattened out toward the bottom, if you remember, about eight inches long.

Purcell:

With a little tube inside the microphone, a “Vassar” mike.

Beranek:

The microphones were very small, very compact. We were assured that ALTEC could control the phases over the main audio range in the loudspeakers, and that we could match them up on the crossover, with a little work and a little filter design, to keep the phases relatively constant. So, our whole skill depended on two things. One was getting everything to move together in phases, and not have any sudden (?) changes, and resonances anywhere. Then, it was in a box in the wall, so to speak, behind this emblem, so we had to be sure that that was completely deadened. We filled it with thick fiberglass.

Purcell:

Four inches of fiberglass in there, and this thing was buried back inside of it to produce as much shielding as possible from the microphone at the podium. The multi-cellular horns were especially aimed somewhat high so that, theoretically, the roll off … the directivity pattern was such that it would probably just strike at the speaker’s head. There was a lot of work with that, and then we said “Well, how are we going to get sound to the front, rows of seats?” We put a second loudspeaker system into the podium.

Beranek:

Then the multi-cellular horn was put in around the podium.

Purcell:

I don’t recall if there was a lot of low frequency in that system. I think there were two cone speakers in there, maybe two 12-inch speakers in the whole array, that is, they were behind the emblem behind the wall.

Beranek:

We tried to preserve the frequency response down to a couple hundred cycles. We didn’t try to get hi-fi, but the system didn’t roll off at 500 Hz which is what you’d get if you used only the multi-cellular horns.

Purcell:

That’s right. In the emblem you see on the wall behind the podium, the earth is perforated metal and the seas are fabric, so some of the acoustic impedance research you had done earlier served us well as far as developing the perforation pattern for the earth surfaces, which was an interesting problem in itself.

Beranek:

But, the system worked very well. The only thing we did later was supplement the central system with a few loudspeakers in the entry way.

Purcell:

Right.

Beranek:

So, imagine this big cone coming down from the ceiling about 10 feet from the floor cut into it partly to make an entry way. But also, some of the delegates sat there as the UN got bigger; because as they had more nations in it, they had to have more space. They started crowding desks into the sides. Then we had to put loudspeakers into the ceilings of those side entrances, and they’d be sitting under the ceiling. To make these work we had to put in time delays. So time delays were introduced into the system, after those speakers were put in the ceilings of these side spaces.

Purcell:

Not digital.

Beranek:

No, not digital.

Purcell:

The time delays in those days were tapes with the playback head spaced away from the record head.

Beranek:

Did you use that as well for the desks; for the speakers on the desks?

Purcell:

Not initially, I think.

Beranek:

No, Delegates had to go up to the main podium in front to use the microphone. There was only one talking point. I’m sorry, not quite: the chairman sat at another podium behind. That’s where the 40 feet got in there, there were two podiums.

Purcell:

Yes, there were two podiums. Well, that was the first major venture of BBN into architectural acoustics and. audio combined.

Beranek:

I hate to say it but we really didn’t know anything. The first time Bolt unrolled those blueprints for the U.N. headquarters that had already been developed, they covered the whole floor of the room. It was frightening, all the things we had to worry about. We potentially had noise between rooms which required noise reduction. We had ventilating system noise. We had rooms that were shaped impossibly. The whole project was scary as the dickens. So, one of the things we tried to do was to learn something about ventilation system noise. In the first place, we didn’t know how much noise fans made, and we didn’t know what the criteria were that you design against; how quiet did the room have to be? So, how much did you have to cut the noise down? The only thing that was known was if you used ducts and lined them, you’d get so many decibels reduction per length of lined duct. That was known already because the people like the Celotex and Armstrong Cork Corporation had developed materials that had been used successfully in public buildings.

Purcell:

Did they actually have a theory, or they had empirical measurements?

Beranek:

All empirical.

Purcell:

So there wasn’t any real work on the theoretical stuff.

Purcell:

Well, the theory fell apart above one kilohertz.

Beranek:

But, Jack talks about a theory, he means you had a simple formula that told you that for so many feet down the duct you got so much attention. This formula was related to the thickness of the material in the duct. It was empirically derived. Now, Morse did come out with a theory, and his theory came out about 1939, but it was based on normal modes and nobody ever used it. Even now the empirical formulas were used. My graduate student George Kamperman came along about then and we decided to learn how much noise fans made. So, we developed a windscreen that worked pretty well inside ducts. We tested it by whirling it in an anechoic chamber, creating it on wind. Then we went around looking for ventilation ducts that had some kind of a hole that you could open up, kind of a plate or something you could unscrew and stick the microphone in and then measure that noise that was inside the ducts. Then, if you go back and look at my early paper on that experiment it says that the noise you get, in the case of the overall noise, is related to the horse power on the name plate of the driving motor for the fan, because the only data we could figure out to take was the name plate on the motor.

Purcell:

So you didn’t even calculate anything about the frequency or revolution or noise due to air speed?

Beranek:

We had no time. We had to design the ventilation system for the United Nations. So, all we did was take the data off…

Purcell:

… the name plate on the motor. Then we determined different “spectra,” depending upon the kind of fan that was used. We had forward curving blades or backward curving blades, or a radial fan. They all had different spectra, so you’d get the data of the overall noise, sort of, for that kind of fan off the name plate. Then you’d pick the spectrum according to the fan you knew was being used there. You could learn that.

Purcell:

What about the level. You knew the spectrum, based on the type of fan…

Purcell:

The noise power level of a fan back in those days, was related to the logarithm of the horsepower of the driving motor. A few years later we got smart and started to consider the number of blades, put five decibels in the octave frequency band where the blade passage frequency, so it was a gradual learning process. But, as Leo says, it all had to be done in a hell of a hurry.

Beranek:

I was just over in Britain and spoke at a British Acoustical Society meeting. Some fellow ahead of me gave a paper on the Beranek method of calculating… or determining the noise coming from fans, using the name plate data, and said it was still the best formula they had!

Purcell:

Well, if you look at what the fan manufacturers give them, and some of the numbers, you wonder if they just took a dart board and…

Purcell:

Yes, there’s a lot of suspicion along that line. I’m very much into that type of work all the time, and question a lot of the data we get from the manufacturers. I’d like to interject a moment that, coming into all this cold, as a graduate student in architecture at MIT, it was a tremendous inspiration to me to realize nobody knew anything about noise in buildings. That meant we didn’t know anything about transmission loss, we didn’t know what a hall did, we didn’t know what fans did, we didn’t know what noise was, we didn’t know what it took to make speech communication possible. What do you do to achieve speech privacy? I mean, there were so many unknowns at that time, but at BBN it was all coming together. Like, every month there was a whole new burst of knowledge and information, which was at an alarming rate and was one of the most exciting experiences I’ve ever had in my life, I have to say that. Working with these guys was some kind of a really fantastic experience, fantastic experience. At that time, Leo… I want to go back, because at that same time or maybe just slightly earlier, the wind tunnel situation came up in Cleveland, and that was a noise control, community noise problem of the first order. Perhaps you might want to address that situation.

Beranek:

Well, the reason I got involved in the Cleveland wind tunnel was I’d written a book on noise control inside airplanes, so at least my name was known in the airplane field. That book came out of my war work at Harvard. The Principles of Sound Control in Airplanes was its name. I was testifying in Washington or something — I forget what it was — I think it was just on noise ordinances, before Congress, and a call came into my hotel to call Cleveland and talk to the head of the NACA, it was called in those days (The National Advisory Committee on Aeronautics, it later became NASA after they went into space.) The NACA directors said to me, “Beranek we’ve got a problem out here that’s unbelievable. We’ve got this big wind tunnel, which is a supersonic wind tunnel with a cross section of six by eight feet, goes up to mach two or two and a half. We put a ram jet into the test section and run it at the same time. Now this thing takes so much electrical power, an equivalent to two thirds of the electrical power supplied to the City of Cleveland at its peak hours. So, we could only operate after midnight, when electrical power usage is down. The first time they operated the tunnel/jet combination was the night before he placed the phone call to me.

Purcell:

And the last time they operated it, for a while!

Beranek:

… and, he said, the thing made one hell of a racket. It not only was very loud…, of course, also, I should have said, they had an expanding cone following the test section, so they’d get a gradual expansion of the air going out, which was, of course, a gradual expansion of the air going out, which was, of course, a big loudspeaker, and that headed off somewhere toward Cleveland.

Purcell:

Cleveland isn’t too far from the test facility, is it?

Beranek:

No, Cleveland is quite a distance away. This is the NACA Lewis Engine Lab that we’re talking about. Well, anyhow, the noise was, by his description, so severe that people thought there was a succession of blowing up of oil refineries or something. The noise apparently was terrible. It shook everything, it scared everybody, they ran out in the streets, all the switchboards went down in the police stations.

Purcell:

How far did this go?

Beranek:

The noise carried over ten miles, and the worst of it, of course, was in the ten miles radius. But, there were a lot of people there, and the city the next morning NACA ordered them not to run the thing again. So, his call to me was urgent “get out here right away.” He said he wanted a meeting the next morning. Also, he said, they had gotten permission from the city to run the tunnel once more, “So you can take noise data, but you’ve got to do it right away.” So, I called Cambridge from Washington and asked Sam Labate and Jordan Bruce to get together all the measuring equipment we had (and I told it went down to very low frequencies, to as low frequencies as we possibly could measure; and we had recording equipment by then) and to get out to Cleveland. Now, it was in January 1950, that this trouble took place. We went there the next day and walked into a conference room that was bigger than this hall, and there were 40 engineers from the NACA present, I should say all their laboratories were represented including the engine lab, and their story was, “If we don’t get this thing quieted, we’re out of business,” because this wind tunnel is our main research facility out here, for the new era of jet engines. So, you must get your data tomorrow.” So, we got ourselves ready that day, and the next day they ran the tunnel engine combination. I forget what time… there’s a lull in the city electrical load during the day and they picked a low power time during the day for us. We got out, took our data along radials, from the facility driving a car around as fast as we could go.

Purcell:

That must have been fun.

Beranek:

We found out where the noise situation was the worst, and studied the radial measurement to learn how it dropped off with distance. That was the only time the facility was operated until after it was quieted. Well, then, what NACA did was to assign to us all their machine labs. We could have anything built that we wanted out two things: One was how to get rid of these low frequency sounds. Around the cone we built a concrete block tunnel and cut holes in the cone that opened into compartments in the concrete block tunnel. By analogy, the compartments were equivalent to capacitances and the holes were equivalent to inductances.

Purcell:

What kind of frequencies are you talking about here?

Beranek:

I’m talking about frequencies of four to eleven hertz.

Purcell:

Subsonic.

Beranek:

Yes. Those frequencies shook the houses. Above 10 hertz we designed another structure — structure is about 30 ft. by 40 ft. which was subdivided into six sections, with specially lined ducts in it. That took out the next range of frequencies, 12 to 200 Hz. Then we went through parallel baffles at the end, to take out the high frequencies, 800 Hz and above.

Purcell:

This was physically how big a muffler?

Beranek:

It was close to 350 ft. long. And I’m talking about 40 ft. wide and high.

Purcell:

What was the power required to run the fans on that wind tunnel?

Beranek:

Well, one thing contributed to the design of the 20 to 800 Hz regions, I learned by accident that if you design a duct lining properly, you can take out a band of frequencies quite efficiently. In fact, I had built a duct that was about a foot square with an acoustical lining in it. The lining consisted of an acoustical material with an air space between it and the duct itself. I’d intended to use this duct for the calibration of microphones. A loudspeaker created tones at one end. The idea of this lining was to cut down on any cross resonances. So, one could have the sound go down through the duct with no cross resonances in the duct. The only trouble was, when you got near 1,000 hertz, on the order of about 30 decibels per foot, and this was a great surprise to me. So, when this Cleveland wind tunnel came up right after I’d gotten that surprise, all I did was scale it up to bigger sizes (it wasn’t one ft. square now, rather 10 x 10 ft. It took the noise out of the next range, above the very lowest frequencies (starting at 20 and going up to 800 cycles). I had to figure out how to broaden the attenuation so it wasn’t sharply tuned. That worked very well. But, we wanted to try it out on a tenth scale, so they built for us in the laboratories a one tenth scale of everything, so we could try out the concept before we actually built the big thing. The speed with which all this was done in the shops was unbelievable. They worked night and day, and we had to figure at some speed to, and then hope what we were figuring was right, because we didn’t know. All we knew as we had a little experience with a one foot square duct at MIT and we knew something about “Helmholtz” resonators… In fact, I almost had a fall out with Professor Ingard who said, if you put in the resonators they’ll sing and make more noise, not less.” I said, “Well, what we’ve got to do is be sure… We’ll put some screen across them so the resonance will be dissipated. He didn’t think it was going to work at all, he thought they’d all sing, amplify rather that dissipate. But that didn’t happen.

Purcell:

What were the flow velocities over the resonators?

Beranek:

Well, of course, they were mock two and above at the point they entered that cone, but expanded fairly fast, so I can’t tell you.

Purcell:

I think it was a classic 19% expansion.

Announcer:

Okay, but it was supersonic…when it was first…

Purcell:

Oh, yes, when it started out at the first hole. But then it got down pretty fast, as you went out, to things that were more like airplane speeds.

Announcer:

It reminds me of a thesis, Bruce Walker’s thesis at UCLA, but it was a much higher frequency he was dealing with than you were dealing with.

Beranek:

Well, anyhow, the thing worked. In fact, we overdesigned; we got it so quiet you could practically stand off the end and only tell by the wind whether things were running or not. We told them in advance that we were overdesigning and told them, “Why don’t we consider cutting back?” I remember the director of the Lewis Laboratory saying, “Look, whether we’ve got a 250 ft. muffler on the end or a 185 ft. isn’t going to make that much difference. We’ve got to be in operation, and we don’t trust you guys that much.” So, we ended up overdesigning.

Purcell:

They figured you were using black magic.

Announcer:

How much attenuation did you get, do you know?

Beranek:

Well, it’s in the records. I can’t tell you from memory, but very, very large amounts. We’re talking about dropping the noise 70 to 1000 decibels.

Announcer:

What was the sound at the beginning of the cone?

Purcell:

Well, the power level on those ram jets was probably about 170-175 dB.

Beranek:

I don’t know. I can’t tell you from memory.

Purcell:

Well, I kind of remember those.

Beranek:

A lot of energy. Incidentally, we had the thing all built, concrete poured, all the mufflers, all the acoustical material, everything in and running by a year later. It just took us 12 month to do this whole thing; they were back in business 12 months later. So, you can imagine the speed with which we operated. Well, then. That led to the next thing that I think was fun. Let’s see now, if I can get my dates straight here. The next project I call “Shoehorning in the Jet Age.” The wind tunnel was in January, 1950, and I’ve gone through that story. Well, this led into the jet age. In the spring of 1956 I received a telephone call from the director of the Post of New York Authority, Austin Tobin was his name. It’s now called the Port Authority of New York and New Jersey (they’ve changed the name), and it operated Kennedy, LaGuardia and the Newark International Airports. Tobin called me at Bolt, Beranek & Newman… Now, in 1956, I was half-time already, at MIT, so I was spending half my day up at Bolt, Beranek and Newman, and the rest of the time at MIT. I used to teach, usually, at noon. He called me at Bolt, Beranek and Newman this particular day and said, I want you down in my office tomorrow afternoon at a 4:00 meeting.” I said I couldn’t do that because I taught a graduate class at MIT from 1:00 to 2:00 PM, and the flight time to New York in those days was over one hour. That would get me down there too late. I said that I would have to get from my class, which stopped at 2:00, over to the airport, followed by an hour and ten minute flight down.

I told him I wouldn’t skip class, there was no way. He responded that there was a flight from there at 2:30, and he would have a helicopter waiting beside the gate that would take me to the top of the building in which he had his office, I would only have to walk down one flight, one story of stairs, go through a door, and I’d be in the entryway to his office. There was only one place helicopters could land (even today) in New York, other than out on that little pad in the East River, and that’s on top of this Port Authority. So, I had my secretary buy a ticket, she brought my car around to wait outside MIT, where I’d come out from teaching. Well, I roared out to the airport, got on the airplane by 2:30; flew down and the plane was a few minutes ahead of time. As we landed, I could see the helicopter below with its blades spinning, waiting. I went down the ramp… of course, we went down to ground level in those days, off the stairway, and walked right over to the helicopter. The pilot was there, calling my name. We jumped in the helicopter, and we flew straight from LaGuardia onto the top of this building, in the middle of New York City, and I was there five minutes ahead of time, for the meeting.

The meeting was to discuss whether BBN could take on the job of determining how much noise a large jet transport would be allowed to make while taking off and landing at the three airports, when fully loaded, in this summertime, at night, when the residential windows were open. I took the job for BBN. I formed a team that worked with me together for the next year, which was Bill Galloway, out here in LA now, Carl Kryter is here at Stanford now, and Lehman Miller who is retired (he’s in Florida). The four of us took on the job of “how are we going to shoehorn in the jet age.” So, one of the first things we had to do was determine the noise created by the prototype Boeing 707 jet aircraft, which had no muffler on it, and compare it with the largest passenger, propeller airplanes operating at the time, both of them at takeoff, fully loaded. Of course, to fully load them lead bars had to be put inside of the planes, to load them up as thought they had baggage, people and fuel on them. That was the way the tests were run. Then, point two, while we did that, we started a set of psychoacoustic experiments in the laboratory. We played back recorded noises from these airplanes and determined at what point the jet planes sounded equally annoying as the propeller planes. We asked people to judge “when do you think they’re equally annoying?” Karl Kryter was in charge of that work because he was an anechoic psychoacoustician. We had loudspeakers in our chamber for that program. We went out to Boeing, they loaded up the 707 planes with lead and they borrowed (I think it was a Lockheed propeller plane, the biggest one they made at that time (I forget what the brand name was on it) for comparison.

Purcell:

Constellation?

Beranek:

Called a Super-Constellation. You’re right. Those were the biggest ones. Then, they flew those on takeoff. We’d have microphones at several positions along the flight path, and take the data. I was very fortunate at that time, because I’d been consulting for General Radio, and they had the first calibrators you could use on the microphones, little portable calibrators, and I got General Radio to let us quick have half a dozen. We then used them on Boeings microphones and on our microphones, to be sure that everything was calibrated the same because we had a mixture of their equipment and our equipment at the different microphone locations outdoors. Neither of us had enough equipment to use all our own. All equipment was battery operated, and you weren’t sure just what the levels would be, so just before the plane would take off we’d all stick on our calibrators and calibrate the microphones. Then, the plane would fly over, and we’d calibrate them right afterwards, again.

So, we had a very reliable set of data, fortunately, on what the noise levels were from these two airplanes. Then, we also recorded it, at the same time, and brought it back for comparisons in Kryter’s psychoacoustic laboratory. We also went out to JFK-Kennedy airport and put microphones at two places, under the flight paths on one of the runways, and took data all day long for different takeoffs, not just from the fully loaded plane, but from whatever took off. So, we had statistics on what people, who lived off the ends of these runways were getting out there. We then developed (or Karl Kryter did, I should say) the concept “perceived noise level (PNDB)”, which you may have heard about. This was sort of a loudness level, only it put a little more emphasis on the high frequencies that the standard loudness level does. We then got our data together. It showed how much one would have to reduce the jet noise to make it no more annoying that the present propeller airplane noise that the people were enduring out there. We had all this together; then we had to tell it to the top people in the Port Authority. But, they had a funny situation to contend with and that was, anything that was printed in the form of a report to them had to be made public.

The Port Authority operated under a public disclosure rule, and they said “If we make public how much noise these airplanes are going to make, we’ll have all these neighborhoods stirred up, and they’ll all be filing lawsuits and everything else to prevent the jet planes from starting to come in. So, we don’t want any reports from you. Everything must be word of mouth. In order to keep our findings secret or that we were even working with them, they decided that they would hold the big meeting with Port Authority personnel in Connecticut, up in Greenwich or somewhere we were to present all our data (we had recordings to play back, to show the relative levels they would listen to.) We flew in on helicopters from different places, which landed at different times to dump us all off, and we went into somebody’s home —a fellow named John Riuley’s home (not the guy who makes books) — we went into his home that evening and we made the presentations to all. Tobin, the Director of the Port Authority, told them, “Okay, we’re buying it. We’re going to have PNDBs as our standard, and the new airplanes will not be allowed to make any more noise than the propeller airplanes do,” in terms of PNDBs, not overall levels. So, this was a big evening for us. The next day, the head people in the Port Authority went out to Boeing and Douglas Aircraft and told them they were going to have to put mufflers on their airplanes, “or else you can’t use these airports.” Well, at first they threatened, “We’re going to bring suit against you guys, because you said a year ago,” and they had it in writing, “these planes didn’t have to be any less noisy than the propeller planes,” and they were using c-scale level measurements, flat measurements as their tests. “What you guys are telling us, in effect, is that we’ve got to have loudness level measurement.” That means that we must pay more attention to the high frequency noise than in the case of the propeller planes, so it means our jet noise cannot be matched to the low frequencies levels of the propeller airplanes. In summary, it meant that the aircraft had to have mufflers. Well, they screamed. Nevertheless, they were told, “You must have suitable mufflers or no planes are going to land at New York airports.” Well, if the airlines couldn’t operate a jet airplane out of those airports, without LaGuardia and Kennedy available; that would be a financial disaster. So, they went into the most frantic muffler development program you can imagine. By the winter of 1957 Boeing had developed the well known multitude exhaust muffler for the first 707s. So, we went out there again, took measurements of the noise with the new mufflers on. We found that the only way they could even make meet the PNDB levels was to climb as steeply as possible after takeoff and then cut back the engine power-level as they flew over the neighborhoods. That flight profile, then, became the standard noise abatement profile: You get up as high as you can, then cut your power down as you fly over the neighborhoods. Then you could put your power on again.

Purcell:

Who made the engines for the 707?

Beranek:

Those were made by Pratt and Whitner. They were Pratt and Whitney’s first engines. They were not bypass yet.

Purcell:

In fact, they had water injection, as I recall, to make steam so they’d have enough power for takeoff, extra power.

Beranek:

They didn’t do that after they put the mufflers on. They could do that. In fact, the military ones all did that, you’re exactly right. But, they didn’t do that after they put the mufflers on. I don’t know why. There was no more water used. So, they were told the conditions under which they could operate: Mufflers and flight contours. Then, Douglas and Boeing had to go to the airlines and tell them what was involved. The airlines were outraged. They said that the extra weight was going to cut down their range, they’d have to put more fuel on, “We can take on fewer passengers, it’s going to make these airplanes more expensive to operate; you never told us this was going to happen! How can we kill off this Port Authority?”

Purcell:

Tobin was a very powerful man in those days, and you didn’t argue with him.

Beranek:

Well, they tried. They said, “Well, okay, when are you going to make it public that you’re going to put this rule in effect, because the day you make it public, we’re going to fight you.” So, they said, well, if Boeing’s schedule of producing these airplanes is to be followed, they will put out so many a week — starting a certain day. “We (the airlines) must have an answer a month before we plan to operate out of these airports”. The airlines, we had by rumor, had a plan, and that was they were going to bring suit against BBN and the Port, claiming that BBN had been bought off to produce these reports — these so-called date and that BBN had never produced any reports. They said there was not a single thing on paper, anywhere. So, BBN certainly had not done any work, or there would be some reports.” Austin Tobin called me on the phone and said, “Leo, we’re going to have to have some reports within 30 days, and they’re not going to be trivial reports, they must be convincing reports.”

Purcell:

His plan backfired, didn’t it?

Beranek:

Yep. So, we started writing, with almost a production line of writing. We had Galloway writing certain points, Miller writing certain points, Kryter writing the psychoacoustic points, I was trying to write the whole, kind of general plan — concept of how you present this to the public. We ended up with drafts. Then we’d fly down to New York with samples of what we were writing, and present it to Tobin and his top people in a meeting room. Then we’d fly back and write some more. We had to figure out how many illustrations and graphics we needed, and have graphics people work. We were working night and day for the month. The day then came to bringing the final draft down to New York, where they were going to type it onto stencils, you know, where ink goes through the stencil… mimeograph… so we had this thing ready about two days, three days ahead of the deadline, when they started their typing. Before we’d type, we had to bring in Boeing and Douglas, have them read the thing and criticize, because we didn’t want anything in there that would get us or them into trouble. We had to at least word the thing so there wasn’t some accidental court troubles. So, they’d ask for changes here and there in the wording. That held us up another day. We were working sixteen-hour days in New York by that time, and we’d even taken down our two draftswomen and our own typists set up down there. We were running a little sub-show. On the last day, the stencils were ready so they ran the pages off. This was just one day ahead of the day these things had to be distributed. Now they said they needed a thousand copies. This comprised two books, each the thickness of a telephone book, containing all the data, all the raw data and everything else. Our draftswomen had drafted all the figures up and the Port Authority had helped us with their draftswomen and typists. We were ready; then they ran this stuff off on their own mimeographs. They had a bigger mimeograph plant than anybody else in New York. Sure enough, we had these two big reports, a thousand copies of hundreds of pages each all run off, but there were no collating machines! So, what they did… they call in… Let’s see what the record shows here. I read, “They said they wanted a thousand copies, we worked night and day putting together two volumes, each over three centimeters thick… these reports had been edited, as I said… the Port duplicated the pages on their stencil-type copying machines in their report department. The machines were slow and there was no means for collating them.

That evening before the release was due, the printing was completed. For collating, the Port called in about 100 of their airport policemen to do the job by hand, in full uniform, bulging with whistles, handcuffs and pistols. Minus only their caps, they went around tables, laying out one page at a time, 1,000 copies, one following the other. The job was done, I think by about 1:00. At 1:00 A.M. the collating was completed, and the volumes were rushed by van to a binding house nearby.” “By 8:00 A.M. a fleet of 100 taxicabs was assembled to deliver several hundred copies of the reports to the New York offices of the airlines, the aircraft manufacturers, the newspapers, trade magazines, important government officials in the two states, various municipalities around the airport, and the federal government agencies involved.” The airlines were unable to mount their alleged charge of improper behavior by the Port Authority and BBN. They had to accept the requirement for mufflers and suffer the loss of range and payload. Most important to us, BBN was not ruined! A few month later, November 1958, the first jet flights took place from JFK (Kennedy) airport. No lawsuits were filed by the inhabitants around the airport, and I firmly believe that these studies and reports shoehorned in the age of jet airline travel. The air industry has never acknowledged that we did anything for them. In fact, they’ve always been mad at us because we required them to put on mufflers.

Purcell:

There are five books of yours that I know of — Acoustic Measurements, Acoustics, Noise & Vibration Control, Noise Reduction, and Music, Acoustics & Architecture. Can you tell us why you wrote those books or, how you came to write them?

Beranek:

Well, Acoustic Measurements just came out as a revised edition this November. Half of it’s been rewritten. It’s now called Acoustical Measurements, to bring in the modern terminology and methods. The word “Acoustics” is something that’s supposed to have sound connected with it; “acoustical” is an adjective against something that doesn’t have sound connected with it. So, that’s why the name changed. Anyhow, the Acoustical Measurements was a result of my war work. I ran, during World War II, as I said, first the Research on Sound Control Group and, then the Electro-Acoustic Laboratory, both at Harvard University. We did airborne acoustic kinds of things — microphones, loudspeakers, acoustical materials, etc. and everyplace else in the world shut down in that area, even Bell Labs, who were devoting their efforts to underwater sound. They had stopped doing airborne acoustics. So, we made all the advances in the airborne acoustics over a period of five years. The advances in the field are what I wrote up in the book; it was the record, really, of what we had done in five years, with quite a lot of money compared to what had been available up to that time in this field, except in Bell Labs. But, they had stopped, so we had the field to ourselves for that period, and there was nothing else going on in England and nothing else going on in Germany. Almost every other acoustic effort was in underwater sound. That’s where the big concentration was. That’s the first book.

The second book, Acoustics, was done when I went to MIT and they told me to teach the course starting the day after I arrived. I then converted those lecture notes into the book, Acoustics. The third one was a result of their asking me to teach summer courses in the new field of noise reduction. Now, noise reduction became important after the famous “drop forge” hearing loss case, where the government ruled that a person who had suffered hearing loss over a long period of employment could collect from the employer. Up until that time, an employee could only collect from the employer for something that happened at that time. If you had something that happened over a period of years before, you couldn’t collect for it; it had to be associated with a particular incident. Well that scared the devil out of all of industry, because many of them had been producing something with noise accompanying the production. They were afraid that they were going to have to pay big sums of money, and there was talk about billions of dollars having to be paid out to employees. Well of course, what happened was the states then put in laws that limited the amount of money any one employee could collect.

Also, employees had to have a sort of before and after hearing test, and most of them didn’t have hearing tests back 30 years ago. So, it got harder to collect. In any event, the result was that MIT was almost pushed into putting on summer courses for industry, and that lead to Noise Reduction, which was the first book that came out as a result of this new age of noise, and the liability for noise-damage to hearing. Noise & Vibration Control was written sort of on the basis that we felt that BBN had collected so much information that we ought to make it available. This was written — this group of chapters…not all people in the chapters are BBNers, we’ve got other people in certain chapters, but Noise & Vibration Control came as a result of that. Music, Acoustics & Architecture was a result of preparing for the work we were going to do for the architect at Lincoln Center’s Philharmonic Hall. I’d actually started on that kind of collection of information on concert halls and opera houses before Lincoln Center was even thought about, but then the Lincoln Center projects brought us more vigorously into the field. We wanted to learn something, because we knew nothing about concert hall acoustics up until that point, except to say that there were a couple halls people liked, and a couple they didn’t. That’s about all we knew. So, that explains the five books. The only other explanation I can give is that I get up in the morning early (I’m usually up at 5:00), and I like to write in the mornings. In fact, while writing Acoustic Measurements, I would go to the library about 7:00, work until 12:00 — five hours in a row and then work no more that day. In the afternoon, I could do research in the laboratory. But, by concentrating periods, shut off from the phone and getting up early, I got a lot of work done. Now I use a PC, I can type right from my brain to the screen. I don’t know if my fingers are operating (I use the touch system and type rapidly), and I find the PC is a great help to writing, a great help to thinking even, because I can think and change my mind and go back and change a sentence, reorder it, move paragraphs, with the greatest of ease.

Purcell:

Have you ever been zapped by losing a page? Or more?

Beranek:

You mean in the computer.

Purcell:

Right.

Beranek:

No, I never lost anything important. No. Of course, I use backup from time to time, and I can’t remember ever being sad about the computer.

Purcell:

That was a very good question; I’m very pleased you brought that out.

Purcell:

That aircraft sound control thing, you were the head of that group, and that was just a bunch of assembly of individual papers and articles?

Beranek:

Well, this book Sound Control was put out, really, on the basis of the first couple years of our war work. Of course, we started microphone work even before the book came out, but that book had to be put out so the airplane companies could quiet their airplanes. And, there was so little information in the field that if you didn’t write a book on what it’s all about, they wouldn’t know how to apply it to their airplanes. So, this was paid for by the government, and it was a rush job, done to help the airplane companies.

Purcell:

Are there any significant, obscure books with your name on them?

Beranek:

Not books, no. Of course, there are some (as there are with Jack’s name, too) reports from BBN. But, most everything of any importance now is in writing. And, much is published only in the journals, but you can find it.

Purcell:

The aircraft noise project you talked about, do you consider that one of the largest projects BBN ever encountered or handled?

Beranek:

Wait, let’s get straight now.

Purcell:

I mean the Port Authority project.

Beranek:

Well, it’s hard to say. Of course, now, BBN now has close to 3,000 employees, and almost all their work is in the computer field. They’re listed on the New York Stock Exchange; it’s a big company now.

Purcell:

I guess I was referring to your tenure.

Beranek:

Yes, during my tenure and in airborne sound.

Purcell:

Following the Port Authority, there was a lot of work done with establishing the parameters for community noise which involved installations for the military, naval air stations, air force stations, fields, aircraft activities. Community noise became a very serious problem. Perhaps you might want to talk a little bit, Leo, about the development of noise control for the jet engine test cells we were doing, and which then led to some work at the aircraft manufacturers, and then the community noise studies done in Tucson, for example, which led to establishing, essentially, a criterion for permissible performance in a community, prior to a community getting upset and responding negatively. You might want to touch on some of that, Leo.

Beranek:

Well, in the l960s, noise became more on the minds of municipalities and people, and I guess all areas of pollution were starting to be thought about. Noise pollution was one of those, and all around the world they were starting to have bodies formed to deal with noise. Publications began coming out labeled “Noise” of some kind. So, in the ‘60s this field was building up. Then we came into the age where the government started financing studies on noise, principally out of Wright Field, and out of a laboratory that was headed by Henning von Gierke, who just retired a few months ago now.

Purcell:

Did he?

Beranek:

The Department of Defense was financing studies of noise and its effect on neighborhoods. In fact, some of the studies, one of the big studies was made around the Burbank Airport here, to find out how people were annoyed by aircraft noise. One of the things that I remember was that they had to shut down a runway to rebuild it so they had to use a runway in a different direction. So, they were annoying a new group of people. We took noise data, before they shut the runway down. Then we took data afterwards, for the new group. Then, we took the data in the old neighborhood after the shutdown. These were questionnaires door to door, talking to people about what they’d observed about the noise. Because their questioning was always done as though they were being asked about everything, not just noise; asked about whether smells or other thing were bothering them. So, quite a lot of information was put together, leading up to the end of the 1970s, on aircraft noise and its effect in the neighborhoods. Some of this came too from manufacturers. We were called in to quiet jet engine test cells at Pratt and Whitney, at GE, Chrysler, Ford and, of course, the big aircraft companies, Boeing and Douglas, General Dynamics and Lockheed, which were also using us for the quieting of jet cells. We had a sort of a monopoly on information in that age, on what it took to quiet big, noisy things. Nobody else was really involved in it.

Purcell:

Excuse me. What is a jet cell?

Beranek:

It’s that cell where you put a jet engine, that’s just been manufactured or is brought back for repair, for a test. You have to run it, on the ground, and it’s usually not far from houses. So, in the cell…quite often it is a U-shaped cell, the air is pulled at one end, the engine is in between, and the air exhausts out the other end. You put your treatment in these two vertical sections, to keep the noise from getting out. That was a pretty big business at one time, until the acoustical materials companies standardized their materials (you could buy it off the shelf and put it in), and you don’t need to have engineers anymore to help you.

Purcell:

It’s interesting that the field of acoustics has promoted a lot in industry in the sense that… to speak privately, for example, in large, open landscape office concepts, so much was developed out of the firm of BBN, how to achieve it by utilizing a masking noise system, partial barriers and the like, so that the manufacturers have now hooked on to that, we don’t do much consulting anymore in those things anymore. Jet engine test cells — I haven’t consulted on a jet engine test cell in 20 years. Like you say they’ve all taken over and everything’s off the shelf now. Audiometric testing is now off the shelf, whereas we used to sit down and design audiometric test rooms and the like. So everything we did we knew eventually would terminate in some manufacturer developing and designing something that would be off the shelf, and it’s been very successful along that line So, you keep working yourself out of concepts of acoustics, and enter new fields as they happen to develop. Now, everybody, I’m sure, is very interested in wanting to hear about Lincoln Center. Of course, Leo can’t give a talk without being subjected to this, so I’m going to subject him to this. Because, while the Port Authority was the first major “accusation” situation, where we didn’t disclose or publish anything, this was certainly the second “accusation,” that hit BBN like a thunderbolt.

Beranek:

It sure did. Well, I don’t know. There should have been a way to handle that so it wouldn’t have come out the way it did. But, nevertheless, we had a lot of trouble. The way this started off was they decided to build a new concert hall in New York; also an opera house. In fact, there were going to be four new buildings put up there — the City Opera in a kind of a theater building, then the main Metropolitan Opera building, the Philharmonic Hall, the Juilliard building, and then there was a little theater, the Vivian Beaumont Theater. So, they hired us to do the acoustics for the whole bunch. Now, the same architects, Harrison Abramovitz, had the whole thing. We had worked with them on the United Nations buildings and we had, of course, very good relations with them after the United Nations opened. It looked as though this was going to start off to be a happy relation. But, if you go back and try to put this story together, you wonder why it worked even as well as it did. To give you the picture, first of all there was an enormous fund-raising project in progress, where they were out raising money from very wealthy people, trying to put together something like $200-250 million to build this whole affair. So, that was one group of people, who were out fund raising and making all kinds of promises about how they were going to put up the greatest buildings ever built, building up people’s hopes, etc. The second thing that happened was, the job of doing the Opera house was selected by Harrison, who was the head of Harrison and Abramovitz, and Abramovitz who had been understudy for him before he became a partner, was given the concert hall. Then it was decided, along the way, not to give them the New York City Theater, but instead it was given to Philip Johnson. Who did the Vivian Beaumont Theater, finally?

Purcell:

Saarinen.

Beranek:

Saarinen. Then Lincoln Center set up a building committee, and it started off being pretty well operated. It was under the direction of a business man they hired full time, who was a very sensible man. He did all the initial planning on how the big the buildings were to be, what their purposes would be. Of course with the committee under him, he was dealing with the Metropolitan Opera, the New York Philharmonic and the City Opera all the constituents who were going to use it and what their demands were. Then the city made parking demands. It was an enormous project to put together, because it was going to be a development in New York City unlike anything that had ever taken place before. If you built it today, the cost in dollars would be several times what it was then.

Purcell:

Didn’t this also involve relocation of the residents, and wasn’t Robert Moses involved with this?

Purcell:

Moses was responsible for everything that was planned in that period of time in the City of New York and its immediate environs. But, whether or not he influenced the design or the location…

Beranek:

He didn’t influence the location or the design, but he might have had something to do with getting the residents out of there.

Purcell:

The clearance was handled by Moses.

Beranek:

Yes, because they had to clear that area. Then, there was subway noise and something had to be done about that, because it was pretty bad; the subway goes right by Lincoln Center. The project was enormously complex that Lincoln Center eventually realized that they had to go at this a little differently, and they started breaking the thing down differently. They also decided they had to have a super committee of leading New York businessmen and figures to oversee the whole thing. So, they had a Lincoln Center… I don’t know what they called it… the Lincoln Center main committee, the Board of Directors of Lincoln Center, and the chairman of which was John D. Rockefeller III. The Committee members were people like the head of CBS and big industrial people in the city, who had their offices there. They had a member of the Rockefeller Foundation who was prominent on the board, and the first project they wanted to complete was the concert hall. So, we had the same problem we had with the U.N. — that we really didn’t know anything, and neither did anybody else. If you go into the literature, you will find acousticians only had Sabin’s formula, which told you how much reverberation a room would have if you knew what was in it; you could calculate the total absorption by counting people, etc. (Even the absorption per person, was badly wrong.) The other information you needed, as to how you shape a room or how many people you could put in it, etc., you could only answer by saying, “Well, let’s copy Symphony Hall,” or some response like that. We also had build up some prior negative feelings toward us, which didn’t help us any. One negative feeling was that the Kresge Auditorium at MIT whose acoustics were not very good for concert music, look at it. It’s absolutely round, like a half-a-grapefruit, and inside it’s the same thing. It was done by Ero Saarinen & Associates, and in an effort to make the thing usable as an auditorium, because with that shape you had nothing but trouble, we hung in some panels from the ceiling. Well, over the stage, which is out where the grapefruit comes down, there’s not much height. So, these panels were not very high, and unfortunately the hall was built, to be a student auditorium but they wanted to dedicate it with a concert. This happens so often. So, they get the Boston Symphony to come in and dedicate the thing, and the Boston Symphony says it isn’t Symphony Hall! “The ceiling’s too low — we don’t like the sound…”

Purcell:

Well, it’s a drama theater.

Beranek:

“The panels are too low, we can’t hear from one side of the orchestra to the other, we don’t have that nice, resounding sound we like… we don’t like the hall.” So, what Time magazine does is write it up as a catastrophe…

Purcell:

Good news doesn’t sell papers.

Beranek:

… so we ended up with bad press on that, and I’m reminded of that when Bing wrote his book, when he retired from the Opera. He commented on acoustical consultants, and he said, “Bolt, Beranek & Newman was no good because Kresge Hall was so bad.” Of course, he’d never been there, he never asked what it was designed for, he knew none of the history, but, that’s the general impression. So, you start off with that negative, and then Jack got involved in something that gave us a lot of trouble. Mr. Szell.

Purcell:

Well, I was also involved with Kresges.

Beranek:

No, forget that. Tell us about Szell.

Purcell:

We were called out to Cleveland to do a high school.

Beranek:

And this was a result of our having been there with NACA, because one of the senior executives who was at NACA was also the head of the school board at this high school.

Purcell:

George Szell was, of course, at that time the conductor of the Cleveland Symphony. We were invited to go out to Cleveland and take a look at an auditorium that was being built for a Cleveland high school, just immediately outside the City of Cleveland. So, I was elected amongst our team members to go out and take a look at the project. We came back, worked with the architect over a period of time, and about two thirds of the stage through completion Mr. Szell announces he’s very unhappy with the present area in which he’s doing the recording, in the Cleveland Symphony Hall. He’s very unhappy with recording, and he’s looking around for a place to record. He spots this new building going up, this high school auditorium, and elects to choose it as his potential recording studio. So, to my horror, I find out that Dr. Szell is going to bring over the Cleveland Symphony and hold a rehearsal. Now, the building isn’t complete yet, the acoustical treatment on the back wall isn’t up and the ceiling isn’t completed, we don’t have an orchestral enclosure, there’s a lot of things of a very mixed disposition.

Beranek:

It was never designed as a concert hall.

Purcell:

It wasn’t designed for a concert hall, it had a 20 ft. high ceiling and… So, why he ever got this notion nobody understands, but I recall walking up and down the aisle with Mr. Szell (A very imposing figure, he always carries a big cane and wears a great coat that makes him appear to be three times as bulky). I’m terribly intimidated by this gentleman, and we’re walking up and down these… [Imitates Szell’s accented voice]. For obvious reasons, but I didn’t want to say that. So, at any rate, I made some remark to the effect that plaster board is several times more reflective than wood, and we’ll see how it works out, give it what we can…I kept giving him assurance that we’d make whatever modifications were necessary to give him some potential for recording capability. At any rate, I think it was about three months later, the building now was about 95% complete, and I’m invited out there to visit with Mr. Szell while he goes up on the stage and…

Beranek:

I thought they were ready to dedicate it, and it was a rehearsal for the dedication. And they were going to dedicate it with his orchestra.

Purcell:

That is correct. They were going to dedicate it with his orchestra. I don’t recall what the occasion was, but I was called back out to Los Angeles, and the associate, Bill Cavanaugh, went out, and Bill was at the rehearsal. I don’t think Mr. Szell was ten bars into the presentation when he slammed his baton down on the floor, stormed off the stage, walking through the auditorium, “Vere ist he!: He was going to kill me, he was looking for blood! Fortunately, I wasn’t there, Cavanaugh’s as big as he is, so Cavanaugh calmed him down. Well, what finally did happen, as a matter of fact, they did do the opening ceremony and things went off sort of all right. I think they got some orchestral enclosures around them, I think we made a few modifications too — I don’t remember the details but he did go on to use that, an empty hall, for his recording, for a number of years thereafter. But it got a bad reputation.

Beranek:

Well, the story that I heard, in addition to what you said, was during one of the rehearsal periods he asked that something be done on the rear wall, put some blanket or something up there.

Purcell:

Right.

Beranek:

I don’t know if it was you or Cavanaugh that was there at the time, one or the other of you, and made the remark, “Well we don’t think you would hear the difference.” Then he blew up. He interpreted that as meaning we thought he was deaf or something! He told that story over and over, all over the United States. He hated us, we insulted him, it was terrible, and I remember just jumping now — Lincoln Center, the day before it opened, the music critic — Irving Kolodin — the music critic for Saturday Review, came to see me in the hotel where I was and said, “Beranek, you’re going to have real trouble, because Szell is going around everywhere, saying he’s going to give you a lot of trouble. If there was any way you could quiet Szell down, your life would be simpler. Well, anyhow to jump back now to the Lincoln Center organization. They set up this committee, and then Lincoln Center had to have a big committee on it, but I’m wrong when I said who head of it was. John D. Rockefeller III and his group were head of the building committee, as time went on. The first fellow I told you about, the businessman quit and left; it was too complicated. Now, John D. Rockefeller III was a dreamer. He was impossible. He didn’t know any business. He had been brought up in a life of luxury and actually didn’t know anything about the real world.

So, he was a very unusual man to put in charge, except that he’d given a big donation toward this $250 million — like $50 million. Then they set up the All Lincoln Center Committee that was over the whole thing, including the building committee reporting to it, and that was headed by a music composer, William Schuman, and William Schuman was a close personal friend of George Szell! So, the plot always thickens, anyway you tell it. You wonder how you ever could get into a mess like this. Well, the story was that we then went ahead with the architect, Abramovitz, and it turned out that Abramovitz was a very weak man. He was frightened to death of Rockefeller, who was chairman of the building committee. He was frightened to death of all these big names who had been brought in. William Schuman — he couldn’t cope with in his thinking at all, so he was a scared kitten in the whole affair, and he was the man in charge of the architecture for the building! His partner knew this Harrison but he didn’t dare take the job away from his partner, now that he’d been given it. So, things started marching ahead and the first thing they had to do was develop was what kind of hall should they build; what’s it going to sound like? So, I took Abramovitz to various halls. Reginald Allen was his music expert and went along. Reginald Allen had been the music director for the Metropolitan Opera, with a very good ear, a fine gentleman, good man to talk to, and he was going to be the consultant Lincoln Center hired to work with the architect. So, Reginald Allen, Abramovitz and I went to these halls, and finally decided we were going to copy Symphony Hall, acoustically.

So, a big discussion came up about Symphony Hall and how many people you could put into it with modern seats, because the seats in Symphony Hall are closely spaced, not very wide. It was built in 1900 and people were smaller then. You didn’t find the group you see here, big fellows, around in those days. The result was we decided it could only hold 2,400 seats, whereas Symphony Hall holds 2,612. So, everything was decided. We were going to go ahead and build the hall with 2,400 seats in it, it’s going to be roughly a copy of Symphony Hall. He developed all the plans, we built a model, we tested a model, and everything was…even an article came out that was published in a house organ that they originated, to have a newsletter, sort of, from Lincoln Center, talking about the merits of this 2,400 seat hall and how they were going to stick with that, and going to have the best hall in the world. Well, up until then things were fine. Then, for some reason Abramovitz had to go overseas. While he was gone, his partner, Harrison, decided that he was going to release the information on what the building was going to be. I don’t know what was going on there, because Abramovitz came back from overseas, practically crying, not understanding why, while he was gone, Harrison called in the press and released the information on the 2,400 seat building. See, there’s a great mix up on this whole affair. So, the story went to press (I’ve got all the clippings on it, even an architect’s rendering, not a drawing, but a rendering, which is more like a piece of art — a drawing in the sense of art drawing) of what this hall is going to look like. I’ve got that today and, in fact, published it in one of my papers, in the technical journals.

This is what they said was going to be built. Well, the next day the New York Times came out with front-page headlines (the New York Times headlines doesn’t go clear across the page, so I mean little headlines) that said, “Lincoln Center Discloses New Design; only to have 2,400-seat hall.” They went on to predict that great trouble will result from this, in a great city you’ve got to have more seats, and New York cannot have a hall this small. So it’s getting late. The deadline for completion of the drawings is starting to come, when they had to have everything done, and get ready to build the hall, let the contract out. The architect, I remember, in January (that would be a year, and nine months, the hall opened in the fall), so in January, I remember the architect calling me down to New York and saying, “We’ve been instructed by John D. Rockefeller’s committee to go up to 2,650 seats. But, we can’t make the hall any longer, and we can’t make it any wider, we can’t make it any taller, but it’s got to have 2,600 seats in it.” Well, so, we said, “All right make the seats smaller.” Abramovitz answered, “No, it’s got to have big seats, we can’t have little seats, nowadays.” So, what they did, then, was to mess the thing up inside, to squeeze in these seats. To do this, there was one feature they didn’t tell us about, and that was that the balconies, which we thought were going to be roughly parallel to the floor. Instead of that, they decided to make very steep balconies, so you could get in the front end of the balcony from, say, Floor One, or get into the back end of the balcony from Floor Two.

They planed the balconies in such a way as to improve the sightliness and squeeze in seats wherever they could, here and there. Well, they got in the 2,600 seats and changed our design, but the trouble was the architect forgot to send up the blueprint to show us the balconies were going to plunge, to be so steep. We had no blueprint after those meetings in January, a year and nine months before they opened the hall, and we didn’t realize the balconies were going to plunge; we thought they were going to be as in the original design. We did know they were going to have some curvature in them, which wouldn’t have been so bad if they hadn’t plunged. Because what happened with the curvature and plunging toward the stage was, the sounds on the stage would follow the curvature up and would hit the rear wall, come back down that same curvature, come back on the stage, and you had a much greater chance of an echo on the stage, which you didn’t want. So, we didn’t know this was going to happen. Then, the first we knew about it, came along about May and we got the final prints to the buildings, and here we saw the plunging balconies. So, Russell Johnson was working with me, we went down and talked with the architect and the architect said, “It’s too late. We can’t change anything now.” We said, “Well, it’s going to give us trouble.” They said, “Well, we can patch it up later.” Well, that was one thing. The second thing was that, because the hall had to have these big seats in it, one had to get more reverberation in the hall by making the ceiling quite high, because if you look at… the audience is the principal absorbing thing, you make the audience bigger and you’ve then got to provide more volume in the hall, because your equation gives you a reverberation time that’s equal to a constant times the volume divided by the total absorption more people, more absorption — the top numerators got to have more volume then. All right. So we had to put the ceiling higher.

Well, putting the ceiling higher really meant that we had to put some panels in there and the only panels we knew that really worked had been used in Tanglewood, and used with great success there. So, we tried to get the architect to adopt the same panel arrangement that we had in Tanglewood, and put it into this hall in the same way. Well, Abramovitz about went wild with this, because he couldn’t see any way to make it look good, he thought. And, great troubles came up over this panel array, and finally he designed a panel array that was not what we asked for, it was not like Tanglewood, but it was one that he thought would look better. Then, we said, “All right, we’re going to have to do corrections later, so let’s hang each row of panels” (and there were some eight or ten rows of them) “on motors so you can pull them up and down, adjust their heights, make the ceiling shape for these panels different, different heights, and also we want the panels so you can tilt them, and therefore direct the sound in different ways. Or, if possible, we’d like to in some ways maybe be able to bulge a row of panels, so it wouldn’t be flat across.” All right. So we had them draw all that into the plane. The next thing we asked for was, “Now, we cannot have smooth walls in a concert hall. There are irregularities on them, of some kind.” Every great hall, including Boston, has niches and scrolls and statues and all kinds of irregularities.

Purcell:

Junk…

Beranek:

… on the walls and ceiling to diffuse sound, so you don’t get what we call the “acoustic glare.” All right. So Abramovitz designed all this. Then came the big day — the day they actually decided to increase the seats from 2,400 to 2,600, we just about resigned. We wrote a very strong letter to Lincoln Center and said, “If you change this design you’re headed for trouble (I’ve got this letter), and we just feel that you should not take this chance; we cannot guarantee that the hall is going to get good.” Well, all right. So, first of all there’s this increase in seats. Second, we didn’t know they were going to plunge the balconies. Third was… now we come to the diffusion on the side walls. Everything was planned, it was going to be on there, and then they got the cost on it, and the building committee, under this great leader of John D. Rockefeller III, said, “We can’t afford it. We’re going to have smooth walls. No diffusion. Like it or not, smooth walls. Okay?” We should have quit. In fact, we should have quit three different times.

But, we believed that as a consultant, you’re supposed to help, you’re not supposed to quit. Then the next level came, which was this motorized raising and lowering so we could quickly adjust things, make things sound better or worse. The motors cost too much. So, they cut those out. Well, then, “Can we have some hand winches?” “No, it’s too dangerous. Something might get loose and crash down on people. It’s got to be fixed permanently.” So, they took away all the variability and aid, “Well, we can always come in there, put up scaffolds, and maybe raise them more afterwards.” Now we’re faced with all kinds of changes from the 2,400 seat thing that we’d done all the studies on, all the models, all the thinking. We knew that 2,400 would work, because it was like Symphony Hall. The new thing, now, is getting to be a very strange animal, very different. No diffusion, plunging balconies, too many panels, no adjustability. So, we had always planned a tuning week, and we thought that maybe we were going to get by. We made some changes during tuning week, and it seemed to everybody there that although the hall was not quite as good as we all wanted but maybe it was going to get by. Then came the great night, and then came double trouble, because, in the first place, they got Bernstein to put together the opening performance, and he decided he didn’t want to use a 100-piece orchestra, he wanted a 200-piece orchestra. Secondly, he wanted to open the thing, not with something that was familiar, like Beethoven’s Fifth, or some nice piece like that, but it had to be some modern thing. Just to give you an idea, in the opening composition they had a piece of railway rail, six feet high, and a guy with sledgehammer hit it at several points. The piece was so loud that everybody’s ears hurt when the whole performance was over! He had three choruses; I would judge he must have had 300 people on stage, singing.

Purcell:

They did Mahler’s “Eighth,” that’s what they did!

Beranek:

But, it was done with all forces, you know, enormous forces. It was just unbelievable. The result was it sounded horrendous. In fact, the newspaper said, “Gargantuan visits the new hall!”

Announcer:

See, that just proves that if you are very difficult to work with, so maybe the hall actually works right, but, if you comprise to what everybody else wants, it’s your fault.

Purcell:

That’s essentially it, yes.

Beranek:

Then, of course, when this trouble came in the newspapers then, and they said how terrible it was, and it was much worse that when we had tested it in the tuning week, with a normal orchestra, because of these great forces and big sound and everything that was going on. Then, of course, the dye was case once you get a bad press. Now the logical thing to do would be to say, “Well, all right let’s gradually approach this thing little by little and straighten the thing out.” First of all, we could see how these panels should be changed so they would sound better. In fact, we’d turned out some tests that we made on them in the hall, that they were causing some loss of bass that we could get rid of and bring the bass back up. That we needed diffusion on the side walls, which now they could put on, which they had cut out. It was clear that we would need it.

This balcony plunging business, something had to be done to cut down the echoes we were getting off this balcony arrangement, which we knew could be patched up. Well, everything seemed under control. We developed our plans; we submitted our report and said, “Now, this is what’s got to be done.” Then, George Szell shows up at the airport and calls Schuman out at the airport for a conference. Szell tells Schuman, “Get rid of those guys. They’re nothing but troublemakers, they didn’t make Kresge work, they gave me trouble in Cleveland, and they certainly can’t make this work.” So, back comes Schuman, who’s the big president, the music composer, and he tells Rockefeller’s Committee and the architect, “Get rid of them and get the best people in the country in to replace them.” So, Abramovitz puts an acoustics committee together: V. Knudsen, P. Veneklausen, M. Schroeder and H. Keilholz. The committee was told by the architect, “I don’t want you to agree on anything. I want you each to write your own report, each member, then take the report that Bolt, Beranek & Newman sent in, give them all to me, and I’ll decide which one I’m going to accept.” Well, it turns out that’s what happened. Three reports came out, ours and two others, and none of them were alike.

Purcell:

Who were the other two written by?

Beranek:

Well, Paul Veneklausen was one of them…

Purcell:

Veneklausen and Keilholz.

Beranek:

Well, are you talking about the reports, or the other committee members…?

Purcell:

Well, who did they call in to write these reports?

Beranek:

Well, first of all. Knudsen was chairman of the committee, Veneklausen, Keilholz and Manfred Schroeder from the Bell Labs, who had never done anything in concert hall work, were the other members. This was all right, except that each of them put in their own report. Abramovitz chose Veneklausen’s solution for the Philharmonic hall, which he tried to make like the hall he did in Seattle, which worked very well. But, if you look at the business of the plunging balconies and no diffusion, if you do Seattle there, you’re going to have trouble. So, they spent a quite a lot of money the first summer. Shut the place down, took the clouds up to the ceiling to get them out of the way, put in some diffusion on the side walls but not very much, and put in the Seattle construction over the front of the hall. The trouble was the hall was much worse. It was so bad you could hardly hear music in the front of the hall, because of strong echoes. So, then the procedure was to get rid of Veneklausen. Then they go choose Keilholz’s solution, and Keilholz came in, he did some more patching, and it made it still worse. Now Lincoln Center’s main committee is very upset, so they fire Abramovitz, fire the whole committee and they bring in Cyril Harris as acoustical consultant, to work with Philip Johnson.

Purcell:

I didn’t know Philip worked on that.

Purcell:

Is this ‘72 now?

Beranek:

It was the architect and acoustical consultant who worked on the theater, across the way; Philip Johnson and Cyril Harris.

Beranek:

It was between 1972 and 1975 — somewhere in there. So, then Philip Johnson came in and said, “Look, the mess we’ve got here with balcony fronts that nobody likes, with improper diffusion in the hall, with acoustic panels pulled up to the ceiling that look like hell…” Going back to 1960, another thing was bad… Abramovitz got to be so disliked by the committee that they said, “We’re not going to trust you to do the interior of the hall; we’re going to hire an interior decorator.” So, Abramovitz, the architect, was displaced two years before the hall opened from doing the final thing in the hall. They hired an interior decorator who did all the lighting, painted the walls dark blue, and gave the whole thing a funny kind of cast. Do you remember the dark blue in there?

Purcell:

Yes, yes…

Beranek:

And I remember Szell rehearsing in there, Szell turning around and throwing his baton down and saying, “How can you make love in a blue hall?!” So, Abramovitz didn’t even decorate the hall thing, if you can believe that! The painting and the lighting and all of that were done by somebody brought in at the last minute. So, still more mess. After the hall’s opening of course, we had been ruined. We should have quit back when they went from 2,400 to 2,600 seats. We’d have saved our reputation at that point. So, Johnson came in and said, “We’ve got to tear it all out and start over.” Cyril said, “That’s a good idea. We can then make it like Symphony Hall.” What they did, then, was to make it exactly like Symphony Hall, they put in the smaller seats, and they got it up to 2,600 seats. They took out these balconies that sloped down and put in the current balconies — that are roughly in Symphony Hall. So, if you look at that picture, and look at the picture Harrison gave to the newspaper in 1959 before anything was started, the two look almost alike. And that’s the sad story of the Philharmonic Hall. There was no way to ever straighten this out, because the position that the architect says is that if you knew it was going to be this bad, you should’ve quit and made a big fuss over it all. Why did you go ahead with this whole thing?

Purcell:

You see, you’re damned if you do and damned if you don’t. It’s one of those situations. You try to be cooperative, you don’t want to quit because then you appear to be a super-ego type of person. But then, like you say, you’re purpose in consulting is to consult. If the client desperately needs something, or wants some change for whatever reason, you try to give them the best guidance you possibly can. You can pound tables all day long, but you can’t make them do precisely what you want them to do. Now, I have a parallel story to this, if I may… Let me just make one comment, if I may, about Manfred Schroeder. He was on that committee for Lincoln Center. Since then he’s come out with this QRD, his quadratic residue which has been popularized now, that diffusion is the cure for the common cold. His diffusers, that I believe are being utilized now, in the Orange County hall, is a prime case of this gone wild, the performing arts center down there, where they have diffusion everywhere, and you have no sense of where you are. The room just seems to go on forever.

Beranek:

But, he did that afterwards. You see, he was stimulated by the work on this committee to think about what things ought to be, and he was thinking about, “Well, can we build a better diffuser?” and he worked on this. Which was wise but it wasn’t there at the time. That was all afterwards.

Purcell:

Well, wasn’t it true that they got the hi-f i manufacturer, Avery Fisher, to pay for that rebuild.

Beranek:

That’s right.

Purcell:

I heard a story that he remarked, just before the remodeling was set to open, i.e., returned to the original Symphony Hall configuration, “I sure hope this works, I don’t have enough money to rebuild it again.”

Beranek:

Exactly right.

Purcell:

I believe I read an article in some popular magazine one time about this situation. They finally came to the conclusion, at the end of the article — that the way they solved all the problems was to go back to your original design.

Beranek:

That’s right.

Purcell:

That’s right.

Beranek:

And they quote me in there as saying, “I hope Harris succeeds; New York deserves a first-rate hall.”

Purcell:

Well, The New Yorker featured it for weeks, on this…

Beranek:

Oh, I’m sure. So did Time magazine and so did Newsweek and so did The New York Times. It was one great mess.

Purcell:

Well, when all this debacle occurred, I was the Los Angeles contingent of Bolt, Beranek & Newman, and at that time I was designing the concert hall for the City of San Diego, which became the Civic Auditorium. I managed to succeed in pulling it down from 3,000 seats to 2,600, after much haggling and wrestling. When Lincoln Center opened, it spread across the country very quickly; then, of course, the inquisition began: “Who do we get to look into what you people are doing on our hall?” They engaged Dr. Knudsen, and Dr. Robert Young, a San Diego underwater specialist. The net result of this, after about seven meetings, was that Dr. Young and myself and Dr. Knudsen were locked in Knudsen’s office an afternoon, while the entire committee from the symphony he San Diego Civic Auditorium waited downstairs in the faculty lounge at UCLA. When you come down, we want a concurrence of opinion on whether we’re doing this thing right or, from all three of you we want some positive directions as to how to make changes.” So here I am, up there with these two gentlemen, and they’re kicking this thing around. They started at 10:00 in the morning but didn’t come out of those offices until 4:00 in the afternoon.

At 4:00 in the afternoon we emerged from his offices, and they had been downstairs drinking coffee and whiling away the time, waiting for some decision that we were all going to be in unanimous agreement. I must say, I was very persuasive and they made no changes. Let me tell about the hall I consulted on in San Diego. They had built the Convair 880 airplane in San Diego. I found out that in order to get the cubic volume right (and Leo had done all the basic research) if you go through all the theory, you’ll find that the relationship of the cubic volume to the area occupied by the seating, plus one and a half feet of the aisles, etc… If you do some fairly precise calculations, you come damn close to obtaining the reverberation time that you want. That was based on your 52-hall studies. So, I had done my homework very carefully, and I found out that we really needed 825,000 cubic feet in that hall, to compensate for the seating area. But, I thought, just for the heck of it, I’m going to make it easy to remember; I’m going to make it 880,000, because the “Convair 880” had been built in San Diego. I thought to myself, I’ll carry that number around. So, I put 60,000 extra cubic feet into the hall, just sort of arbitrarily. I had a little safety measure in there, and I could buy another tenth of a second if necessary, at any rate, because you’re fighting for tenths of a second with that kind of audience size. Well, the net result of the whole thing was that Bob Young insisted there was too much cubic volume in the design. I then made a concession to bring it down to 820,000 cubic feet, and he conceded and that was the major concession… The hall got built, it has all the wiggles, it has all the clouds, it has the 2,600 and it works and has been very successful, which proves one can design correctly. I’m happy to say.

Purcell:

But your 880(000) starting out was a negotiating point.

Purcell:

That’s right.

Purcell:

Well, after hearing all these horror stories of modern concert hall construction, etc., you wonder, how were the old classic halls built? Were they just dumb luck, or were there people who somehow intuitively knew what they were doing?

Purcell:

I think there was a certain amount of dumb luck, but I think also that the thing that mostly favored them was, they were rectangular structures, they were highly ornate in producing diffusion, they seldom seated more than 1,200 or 1,300 people. Our economics today dictate 2,500-3,000… 5,600 seats, here, for example, in the Universal-MCA amphitheater. That’s the kinds of things we’re dealing with today, and if you look at the simple laws of physics, a guy sitting in the third row, you’ve got a 65-70 ft. ceiling, your roundtrip sound wave already exceeds the potential echo condition by about 35-40 milliseconds. So, you’ve got a built-in echo condition. You’ve got all these problems to deal with. You’ve also got… to get 110 or 105 decibel inside several hundred thousand cubic feet is an extremely difficult task. It’s almost a physical impossibility. So, the larger the halls get the more echo potential, the lower the level, the more delayed sound occurring from remote wall surfaces. Everything goes to hell. Whereas, back in those days, the Vienna hall, the Grosser Musik Vereins Hall was… what was it? Fifty-two feet across and 33 ft. high? You see, you’ve got the comfort of a living room.

Purcell:

Symphony Hall wasn’t accepted right away anyway, was it?

Beranek:

Well, let me talk a little bit about this subject. I’ve done quite a lot of studying on this, even recently. I’m getting ready for a paper I’m going to give in Japan. I’ve decided to build this paper in Japan around the successive ages of halls, starting off with the first halls being what you might call the ballroom/concert hall, the music/concert hall, the palace. Those are almost invariably rectangular, relatively high-ceilinged, and full of gold and so on, gym wax all over the place, carvings and pictures on the walls, frames, mirrors.

Purcell:

Wood and plaster.

Beranek:

Well, there wasn’t all that much wood. They always talk about wood. Mostly they were plaster. One of the big mysteries in this whole…

Purcell:

It’s on a lathe isn’t it? On a lathe…?

Beranek:

On lathe, you’re right.

Purcell:

How thick was the plaster?

Beranek:

Oh, it was usually standard thickness.

Purcell:

An inch and a half, maybe two inches.

Beranek:

That was a design. In those days the orchestra sat in the room (there was really no stage, or if there was it was a small six or one-foot high stage that would be put in), and played to a small audience that was all on the same level. There were no raked seats or anything like that; it was a ballroom the rest of the time. So, that brought us, then, up to a later time. The latest hall in that period was really the Vienna “Grosser Musik Verins hall,” which holds about 1,600-1,700 people, and it’s just full of things on the side walls. There are statues and niches and balcony fronts, the orchestra is on a stage and around the orchestra are all kinds of stuff. The ceiling is highly coffered and has large chandeliers. That hall is small, because the seats are small, in addition. So that the cubic volume is small (I think it’s around 535,000 cubic feet, as I remember) and holds 1,600-1,700 people. That hall has got a good reputation. It’s been there a long, long time. The other great hall, that was bombed out in World War II, was GEWANDHAUS Leipzig, called “Neues,” or new, because there had been a previous Gewandhaus. It held the same number of people and had a little different appearance. It looked more like Symphony Hall, didn’t have all these statues. It had a very good reputation, but, again, its seating capacity was about 1,600 people. In fact, when I made my book study, if you go to one part of the book, you’ll find a tabulation of halls in continental Europe, and the average seating capacity of 47 concert halls in continental Europe is 1,300. Then you go to England, the United States, South America, Israel, and Australia, and the average seating size is 3,000, today.

So, you’re faced right away with this size problem. Now, what happened in Boston, which is a hall now that has a very good reputation… in Boston prior to 1900 they had a hall called the Music Hall, which preceded the present Boston Symphony Hall. It was located downtown, the building is still there. About 1890 the city told the Boston Symphony Orchestra people (Major Higginson was their head) that they were going to take the hall by eminent domain, and put a street through where it was. So, they had to look for another place to build a new hall. They went out where the present hall is, what is called the Back Bay, and bought a piece of land no bigger than the hall (I never understood that; there’s no place around it for anything). First, they were going to build a Greek amphitheater with a cover on it. That was the architects plan. McKim, Mead and White were the best architects in New York; they had done some wonderful work. They did the Boston Public Library, which is a beautiful building. They engaged McKim to do the hall. So, Higginson took his plan to Europe, to various musical people he trusted (all of music was in Europe in those days; America was primitive in 1900, by comparison; or, this is a little before 1900). He was told by everybody, “Don’t build a hall like that. Anybody who’s ever tried anything like that has had utter failure. Discard the plans.” So he came back.

The city decided to delay taking this land immediately, so it gave him a couple more years. He told the architect that he should go ahead and make a new design. He told the architect, that they would make a trip around Europe, and figure out which hall they liked the best, and copy it. So, they went around, they decided they liked the Leipzig Gewandhaus the best, with its 1,600-1,700 seats. They came back, but Higginson says, “I don’t want 1,600-1,700 seats, I want 2,600 seats.” “So, what we’ll do then,” the architect said, “is we’ll multiply every dimension by 1.3, because 1.3 that gives you the ratio of the seating area, if you say 1.3, that is the ratio of 2,600 to the seating capacity is in the Leipzig Genwandhaus.” So that was the way they were going to go. But, in the meantime, Wallace Clements Sabin had made his study at Harvard, associated with the original “Fog Art Museum” (that building is no longer there), and had evolved the reverberation formula. So, he then applied his reverberation formula to the Leipzig Gewandhaus (he had the blueprints), applied it to the old Music Hall, and this new, blown-up 1.3 thing. He found that if they did it, it was going to sound like a big gymnasium — l.3 wider, longer and higher, and it just wasn’t going to work. The reverberation was going to be over two and a half seconds, and they were looking for something more like two seconds. Sabine said, “You can’t build that building that way, you’ve got to do something else.” Higginson and the architects asked “Oh, what the hell are we going to do? Because we’re faced with this taking the hall by eminent domain, we’ve got to have a place to play, and we’ve got the money raised.” They had had a fund-raising campaign, raised half the money, and mortgaged for the rest. Then Sabin made his big decision. First of all, Sabine’s first big decision was to tell them not to build the 1.3 size. The second big decision he made was, ‘‘why don’t you copy the old hall — The Music Hall? The only difference we need, I think, if you want extra seats, is that instead of having the stage inside the end of the hall, break the end out, move the stage out, you get more people on the main floor (the old hall held about 2,400), and this will get you up to the 2,600 you want. I don’t think extending the stage that much is going to make that much difference. Copy the old hall.” Well, that’s exactly what they did, and if you have a picture, standing on the stage in the old hall (and they’ve done it), and if you take the pictures available of the new hall, the two look exactly the same, looking back. The only difference is the change in the front of the hall, where the stage is.

Now, the old hall, again, was modeled back as a kind of a blow-up, slightly, of these European halls, particularly the “Grosser Musik Vereinsaal.” They could get up to the 2,400 seats with the small seats, and not have any troubles yet. Now the new hall in Boston which opened in 1900, did give them trouble. Musicians came over from Europe. Accustomed to listening to 1,500-seat halls, they came into the Boston Symphony Hall with its 2,600 seats. The orchestras were 90-players in size at that time, so they said that in the new hall the sound’s not loud enough. “It sounds thin and weak in here.” The hall had a bad reputation. In fact, the reviews on the hall that came out, even two years later… there was a review written by William Apthorp, who was the leading critic in Boston at that time, which says, “The only way in which critics and musical experts agree about this hall is how bad it is,” condemning the Boston Symphony Hall that way. Well, of course, as time went on, they increased the orchestra size from 90 to 105, these musicians in Europe, who were making all these smart remarks, started traveling, running into big halls in England and big halls in the rest of the United States, and began to understand that big halls did sound different. And, of all the big halls they heard, Boston was the best. That’s the way it stands, as far as reputation goes, today Boston is the best of the big halls, and the “Grosser Musik Vereinssaal Ferelnzhall” in Vienna is given the reputation of being the best of the 1,500-seat to 1,700-seat halls.

So, times change. Now it’s being praised, because of its quality for its size. Now, coming back to the change in the Philip Johnson/Cyril Harris hall, it’s been all for the better. That hall… I was just there a week ago and heard two different orchestras, quite a variety of music, including a Tchaikovsky and a Shostakovich. I forget what else interested me. The hall sounds quite good now. It’s a little large, but there are no echoes, the reverberation sounds clean and the sound has a good bass in it and is quite pleasant. So, the original design we made was a good design. Carnegie, on the other hand, which had a great reputation for its sound, they decided they had to make it look better. The front end of Carnegie is a patch-up. They decided to restore the proscenium end of the halls to the way it used to be in 1890. It used to have a curtain down about half the way between the top of the proscenium and the floor. Also there used to be a hanging ceiling behind that curtain; they threw that away. Then, the upper part, there was a hole up there that they had used one time for some kind of a movie production. It was quite a big hole. They plastered the whole thing over and made the whole thing look pretty, they painted it. What you see now is nice proscenium. The walls around the stage goes up straight in the back, and then over toward the proscenium. This means a kind of dome over the heads of the orchestra.

Purcell:

It’s half a dome.

Beranek:

Half a dome. I sat in there a week ago, too. I went to two concerts there, also. It’s nothing like the old Carnegie. Now the orchestra sounds like its way off somewhere. There are no supporting reflections around anywhere, and it’s getting rather bad reviews as time goes on. The reviews start off that way, because nobody wanted to offend Isaac Stern, who had saved the hall. But, now the feeling is that something is going to have to be done. We’ll see what they do.

Purcell:

They’ll probably put a curtain down over the proscenium, and hang the ceiling back.

Purcell:

Who is the consultant these days — for Carnegie Hall?

Beranek:

Carnegie Hall used an Israeli consultant, and I can’t say… he went home; his wife got sick, and he hasn’t been seen since.

Purcell:

Is that Meltzer?

Beranek:

Meltzer, yes.

Purcell:

Weren’t there changes under the floor to isolate the subway noise? Didn’t they go to take out some of the wood flooring, or put beams under the…?

Beranek:

This is Carnegie now?

Purcell:

Yes.

Beranek:

Yes, the subway noise is way down. I was very pleased with that. The subway noise had always been very troublesome there.

Purcell:

And also, it destroyed some of the resonance from the floor, mightn’t it?

Beranek:

I doubt it, I doubt it.

Purcell:

It’s possible, though.

Beranek:

I doubt it. The trouble lies with the changes in the…

Purcell:

In the source end.

Beranek:

In the source end. You can hear it, clearly.

Purcell:

Would you comment on… whatever they’re called… concert halls in which there are electronic tuning methods used for resonance…?

Beranek:

There are so few… one of course is the Royal Festival Hall in London. They had a mess there. I explained why, which is one of the things I feel is one of my major contributions to the field. People did not understand how much sound an audience absorbed. Festival Hall was, indeed, the earliest halls built after World War II, and people thought that you could count the number of people, and that would tell you how much the audience absorbed. Actually, people behave more like a carpet: It’s how much area they cover. So, if you make bigger seats, with the same number of people, you get more absorption because they cover more area.

Purcell:

There’s one more important facet besides the seat size, and that is the code requirements for fire exiting. Because at the end of every row of seats you’ve three and a half feet of body, you’ve got an aisle and you’ve got three and a half feet of body. So, as the aisles got wider, those three and a half feet of body were suddenly… they were laid up horizontally, on a flat surface, do you see? So, you’ve added a tremendous amount of absorption, not realizing… for fire code alone… then, when you go from a 17-inch seat, a 17-inch wide seat, which was the standard throughout all the European, and go with the 21-[seat], which is our American standard, we’re talking a 20% increase just with the seat width. So, just to get the same number of people in, to meet the comfort requirement, the economic requirement for a greater number of seats, and the fire code requirements and the existing conditions, these things all multiply to have a very serious adverse effect on the quality of the hall.

Purcell:

Also, the upholstering of the seats is larger. If local jurisdiction’s flush with cash, they’d have fully upholstered seats front and back and under.

Beranek:

They’ve been backtracking on that and putting in new seats in many of these halls.

Purcell:

What about seasonal clothing changes.

Beranek:

There’s not much evidence that that audience clothing is terribly important.

Announcer:

There’s a coat room.

Purcell:

What Leo did, in order to establish these parameters, was to carefully measure the cubic volume of every hall, the reverberation characteristics of all the halls that he studied, and to do a very carefully documented, dimensional analysis of every seating occupancy area. You’ll find in his book there a very interesting composite of the V over S, which is the cubic volume divided by the seating area. It comes out to some kind of a constant divided by twenty-one, which it is. I can do a reverberation time on a hall in about fifteen seconds; I can mentally go through it. So, he’s made it very easy. It’s a very good, very close first approximation to getting the cubic volume related to the number of seats.

Beranek:

Getting back now to Festival Hall: Because of this larger absorption, due to stretching the people out and having the exposed edges, they did not take into account that was going to cut the reverberation time. Thus it was made too low, they should have brought the ceiling up to give you more volume because, again, if you increase the denominator of your Sabin formula, you’ve got to increase the numerator. The numerator’s volume. They didn’t do that, so they ended up with much too low reverberation time. Secondly, they believed too much in this word “wood.” They put a lot of wood in that hall. The result is there’s no bass in it to speak of, because wood absorbs the bass. Any good hall — Boston, “Musik Vereinssaa”, the old Gewanddhaus — were plaster, heavy walls, not thin wood. So, that hall is very deficient in bass. What they’ve done is to figure out an electronic means of improving it, and at a great cost they have installed microphones around in the ceiling, loudspeakers which you can’t see so easily where they’ve done it, all over. A microphone in one part of the ceiling will feed a couple of loudspeakers. A microphone back here will feed some loudspeakers over there, and without that they’ve built up an artificial reverberation. They call it “assisted resonance,” and it does make the hall sound better. It’s not as good as the real thing.

Purcell:

There’s been a spate of articles recently about temperature effects, what people have considered relatively minor variations in temperature can completely affect the character of a hall. Do you subscribe to this view?

Beranek:

Well, humidity is more important than temperature. You sure you’re not talking humidity? Because, they don’t vary the temperature very much; people can’t stand much temperature variation. I am not familiar with temperature articles.

Purcell:

Because the speed of sound is affected by humidity.

Beranek:

No, humidity affects the absorption of sound waves when traveling in the air.

Purcell:

Not the reverberation, it’s not based on…

Beranek:

You see, if the air absorbs more, then the traveling waves that make up reverberation will be absorbed more. At lower humidities you get more high-frequency loss than at higher humidities.

Purcell:

The Orange County Performing Arts Center has gone through a number of changes, I understand, as far as the sound goes. How does it rate now?

Beranek:

Well, of course, it’s hard to get ratings on these things in a hurry. It takes a long time, until they’ve been used several years and different orchestras play and people get used to it, etc. I’ve gone there and listened, and I’ve only been able to listen from two places, because I did it only in one evening. I was down on what’s called the main level (it’s called the “parquet” or something), and then up on the first level above that, Tier One, above. It’s very interesting. That hall has very good quality. It does not have the kind of reverberation that Symphony Hall has, because of the way it’s put together. I would say that it is likely to be a model for later halls, because they’ll refine that kind of multi-tiered design and I think will make it work pretty well. We have to have an answer to these bigger halls. See, that hall is now running close to 3,000, and this is an experiment (because the only way you can do it is with an experiment), where you try to make it seem like a group of little halls, four little halls, inside of one big one. It doesn’t sound like Symphony Hall, but I don’t rate it as a bad hall. I was rather pleased with it.

Purcell:

Do they use the electronic stuff in there?

Beranek:

No. No, there’s a sound system there, but not for concerts. They use it for jazz, or rock or whatever they call that stuff nowadays.

Purcell:

When the Acoustical Society had a meeting down there, I went to that meeting, and they said that they had done an awful lot of testing. There was an Australian fellow involved…

Beranek:

That’s right. Marshall.

Purcell:

An awful lot of testing… a model, and spark gaps and so on, to assure themselves that the actual construction of the thing would… they had modeled and measured correctly on this thing, to make sure there wouldn’t be troubles.

Purcell:

Well, all major halls today really necessitate some acoustic modeling.

Purcell:

Could you comment on that? I know when you work with a model you have to work with the speed of sound changing or something?

Beranek:

They change the gas in it. The speed of sound is the same. The problem is that the absorption gets… when you model; you’ve got to increase the frequency. Then, because of the way the oxygen-based air — gas — behaves at higher frequencies, you get a lot of absorption there, in the gases that the sound travels around, which you don’t get when you’ve got the full-scale hall. You get some of the high frequency absorption but nothing like you do in the model. So, what they do then is change the gas, use nitrogen or one of those.

Purcell:

If you scale down the size of the hall, you don’t change the speed of the sound…?

Beranek:

The speed’s the same, you change…

Purcell:

You change the frequency.

Purcell:

Oh, I see.

Beranek:

You change the frequency by a factor of ten if the model is one-tenth size.

Purcell:

But the velocity’s the same.

Beranek:

Yes. You go a factor of ten and then you put in a different gas, to get rid of the absorption. Those are the two big changes. Then you’ve got to scale all your acoustical materials, and you scale people… everything has to be scaled to be the same.

Purcell:

What kind of gas…?

Beranek:

I think its nitrogen, I’m not sure.

Purcell:

Well, nitrogen is almost the same as oxygen.

Beranek:

But it doesn’t have that loss in it, though.

Purcell:

Helium?

Beranek:

They don’t use helium.

Purcell:

Would you talk about the sound of the outdoor amphitheater?

Beranek:

Well, this I’m not as good at talking on. You’ve done outdoor amphitheater work, haven’t you?

Purcell:

Yeah.

Beranek:

Maybe you can answer the question then.

Purcell:

Well, I suppose one that we’re all probably familiar with here locally is the MCA-Universal amphitheater; many of you have been to that when it was an amphitheater. It originally started out as a 400-seat, at the end of the program.

Purcell:

The capacity of this, if I may say, is around 1,500-1,700…

Beranek:

What’s she talking about?

Purcell:

Universal? The one that you’re talking about.

Purcell:

The one that is being designed now, that we’re interested in.

Purcell:

I see. Seventeen-hundred seats? It has a very good chance of working — excellent chance of working. The major problem with outdoor amphitheaters, of course, is we’re highly dependent upon acoustical reflection from sidewalls. We localize, we tend to localize because our ears are located in a horizontal plane; we tend to localize on horizontal sounds, so we want that kind of energy to come back into us, which does not exist in an outdoor amphitheater, unless you have some high walls. You don’t have any acoustical reflection from the sky. All the energy incident upon the ceiling continues on and is absorbed, so it’s lost.

Purcell:

May I say, the seating part is like a Greek amphitheater, similar to that, without the background staging of the Greek theater.

Purcell:

The closest thing I can come to, 1,700 seats, is the Santa Fe Opera, which I worked on, in Santa Fe, New Mexico. That was an amphitheater. There, I tricked the amphitheater by extending the canopy of the orchestral position some 25 ft. beyond the orchestra, so it extends the canopy back as far as the canopy can be useful in getting acoustic energy reflected down into the audience. Then, coincidentally, there’s a balcony at the back, which I also took that canopy, wrapped that up higher, and it took over where the front canopy left. So, there’s really about a 60 ft. space in the middle that is open to the sky. But, again, it has high walls. It’s been very successful, and very well received. It has an excellent chance of working, with 1,700 seats — a very good chance of working.

Beranek:

See, the Greek theater (Epidaurus was a good example) was also very steep, as you recall, on the hill very steep. So, people get the sound as close to the orchestra as you can get them, without putting them on a solid wall, vertically. That helps, but secondly, there is a back to the stage… now, you say you’re not going to have any back at all?

Purcell:

No, it’s a very deep, deep stage.

Beranek:

Well, that could give you some trouble. But, of course, you’re going to do opera there? Is that why it’s so deep?

Purcell:

No, a pageant.

Beranek:

A pageant. Well, I’ll bet you they’ll open it with an orchestra.

Purcell:

There’s a very good chance they’ll amplify it. They’ll be doing everything electronically.

Announcer:

This sounds like a theater that’s yet to be built.

Purcell:

It’s in the process. We’re just ready to get into it…

Announcer:

Where?

Purcell:

Northern California.

Announcer:

Is this for dramatic presentations?

Purcell:

Right.

Announcer:

I hope you’re in an area that does not have much noise, because, having spent 11 years working at the Mann Music Center in Philadelphia, with the Philadelphia Orchestra, and having spent most of my life attending concerts at the Hollywood Bowl and other things, the major thing that you’re actually fighting, in the modern day, is environmental noise. It’s not so much the sounds within the theater that are a problem.

Purcell:

Yes. It’s a gorgeous outdoor amphitheater at the foot of Mt. Shasta, and we have absolutely no outer noise, except an airplane at times.

Announcer:

At times. And that can be a problem. Those times tend to be 20 or 30 times during the evening if you’re not careful.

Purcell:

We have that under control. That part is under control. The outer noise business is not a problem.

Beranek:

Well, that’s very fortunate, because one of the reasons the Greek theaters worked was it was quiet in those days.

Purcell:

Also, as you pointed out in your book, for dramatic presentations in the Greek theaters, the players frequently had masks into which small megaphones were mounted.

Announcer:

I would like to ask both of you if you think architects these days have any better education or awareness of acoustics than they have in the past.

Beranek:

Well, you know, awareness is not the right word. They’re scared. This Philharmonic Hall thing scared the hell out of most of them, and they are paying more attention to what the consultants say to do than they used to. They’re also willing to work on some experiments, as the Orange County Performing Arts Center there is, at “Segerstrom Hall”, in an effort to try to do something that will work better in these sizes. So, I’m more encouraged by at least certain architects than I would have been back in the ‘50s.

Purcell:

We have some architectural clients who are very conscious of this type of concert hall design or music acoustics, if you will. The architect that did the local, Occidental College here, which we happened to work on, they were into a financial situation, so did the college. There simply wasn’t enough money to do the project the way it should have been done. It was severely cut back. It has a number of shortcomings, and the architect was very concerned when he set out to do a good job and, in actuality, he couldn’t finish it. We’re running into some of the same problems at Whittier College. They started off with a grandiose idea, thinking the whole hall is going to be completed with 5/8” gypsum board, which, of course, is a low-frequency energy absorber. When I came and told them they had to have two and a half inches of cement asbestos or concrete, it frightens them. All of a sudden costs skyrocket, cubic volume has to increase, and what sold the whole project initially as a fund-raising campaign becomes an unreality. Those are some of the things we’re facing all the time in this field. Yes, those architects who are doing those kinds of projects, they do call consultants in now. We get a tremendous number of calls on those projects, and I think they’re more aware of them. They don’t know what to do with them. But, the architects we work with are listening, to the extent that they can. It’s the dollars that always kill us.

Announcer:

It’s so common. Last year it was more with recording studios and that sort of thing. It’s so common to be told, “Well, we had an acoustical consultant and he said we should do this and this and this,” but they left it out.

Purcell:

Not unusual.

Announcer:

Dr. Beranek, we’re closely approaching our time limit here. Could you just spend a little time on what you see the future is and how we’re going to get there?

Beranek:

Well, there are all kinds of answers to that question. Of course, one area that we’ve been hoping we could do better in is amplified sound, eventually, as halls get bigger. We almost have solutions that can work, and I don’t mean only in adding reverberation, but adding more sound to the source. For example, one case that almost works is at Tanglewood, which is a summer hall. It has 5,000 people under cover, and then it’s considered a bad night if they don’t have another 7,000 outside on the lawn. So, its outdoors, and you’re talking about an audience of 12,000 people. On a good night they’ll have 16,000, and they’ve got to hear out there. So, what they’ve done is take the very finest sound system money can buy today and put up on the outside edge of the enclosure. They’ve put up five different loudspeaker setups — clusters — and people are not objecting to it. Now, it’s not as good outside as it is inside, for all kinds of reasons. There’s no reverberation, etc., but you have the feeling that somehow we’re going to make progress in this area.

Now, in the Great Woods, which is south of Boston, which was put up a couple years ago, is another kind of Tanglewood, only it’s got much more people undercover, they didn’t want so many outdoors. So now they’ve got loudspeakers inside too, and this has not worked out as well. Part of the reason is the hall is seldom full, because they can’t attract the big audience to a symphonic concert in Great Woods they attract to a concert in the Berkshire Mountains in the summer. So, you can’t really tell how well it’s working, it just doesn’t sound quite right. That hall is maybe half full most of the time, it’s especially a problem because it’s got concrete floors and upholstered seats. This is unusual for a concert hall. But, I have hopes that somehow electronics is going to help. The only other thing we’ve got now is the multi-layer vineyard type where you build a bunch of little halls within one large hall as you’ve got out in Orange County. Now, two halls have been built in Spain, one of which has 3,000 seats, I think, which is reputed, now, to have gone one step further than the Orange County Hall, in terms of what the architect could do, what they’ve learned from Orange County, that is supposed to be an improvement. I haven’t gotten over to hear it yet, it just opened recently. I’d like to know how that one has worked out. An older hall that’s got a very good reputation now is the Berlin Philharmonic, which also is a vineyard type hall, but it’s constructed in a different way. They have people all around the orchestra; there’s not a proscenium, as there is at Orange County. It’s only for concerts, there’s no theater ever in it, no ballet, and they have people on the back side of the orchestra, the sides and the front. Now, if you can get used to sitting on the back side, and don’t worry that you can’t hear a person singing or that can’t hear the piano when the piano board’s up.

Purcell:

You lose the first violinist too.

Beranek:

Well, the first violinist comes through fairly well even though they face out, don’t they? But, the other side of the conductor comes through fairly well. The French horns face the wrong way. If you get used to a different kind of orchestra, it sounds pretty good.

Purcell:

There’s another problem: You can’t fall asleep. It’s very embarrassing, because everybody’s staring at you.

Beranek:

But, if you sit on the right side of the orchestra, and the front sides, as you usually do, it all sounds very good. So, I have hope that maybe this vineyard thing can be made even better than the experiments we’ve seen, and maybe amplified sound will help. Now, the next thing that’s going to help us, principally with Japanese research… they’ve apparently decided to put a lot of government money into research on how to simulate the acoustical conditions in a model, in terms of being able to play music inside, then listen with earphones, little “men” with earphones in their ears, and they’re making quite a lot of progress in improving this technique, of listening to a hall before it’s ever built, listening to the model. I think that will help us. The problem with the model is how to simulate the full orchestra, with each instrument recorded separately, but all playing together, like an orchestra. They haven’t been able to do that yet.

Purcell:

Sort of along that subject, do you think the multi-purpose hall can work? Or is it just trying to be all things to all people and can’t work well for any of them?

Beranek:

I don’t know. Are there that many good, all-purpose halls?

Purcell:

No, they all have a drawback of some kind. I mean, is not good for symphonic music, and it’s to put on a vocal presentation or a in the Long Beach Civic Auditorium, and it kind of falls apart. You simply have to go to electronic amplification. Put a symphony orchestra in there, it’s quite good. They can’t do all things.

Announcer:

Aren’t there some with adjustable acoustics?

Purcell:

Yes, there are. The hall at Occidental was supposed to have adjustable acoustics. It was just completed about six months ago. They haven’t even done the final checkouts yet. They were supposed to have, but they ran out of money again, and that’s the common situation.

Purcell:

You think that’s something that could work?

Beranek:

Well, they have used adjustable curtains down at the Orange County Performing Arts Center. They’ve got curtains that come up and down.

Announcer:

They also have them in Davies Hall in San Francisco, and also in Thompson Hall in Toronto. But, I understand they never use it.

Purcell:

They have to know how to use it.

Beranek:

Well, even when I was down at the Orange County Hall, in rehearsal, they ought to put them down, bring the curtains out of their hiding, to make the hall more like it is with people. I was with Jerry Hyde there, and Jerry said, “No, they don’t bother.”

Purcell:

The Spokane Opera House is a project I worked on, completed in 1974. Backstage, at the stage manager’s position, I have a whole series of buttons to push for various things — how many buttons to push for opera, how many buttons to push for symphony orchestra — to adjust the hall to the conditions that I think are sort of optimum. Those all got installed. It’s an interesting hall.

Beranek:

Do they push the buttons?

Purcell:

They push the buttons. They use the buttons.

Announcer:

May I ask… when you push a button, do wooden levers come out and all this? What happens when you push these buttons?

Purcell:

The entire ceiling is a series of wood slats. Remember the United Nations?

Announcer:

Yes.

Purcell:

All up above there are a series of acoustical reflectors, which are actually inverted concrete disks that are four inches thick, and they serve as the primary acoustical reflectors. Then, in between all of those, are draperies which, if you punch button one, track one, the drapery extends. You push the there button, track one retracts, so we change and alter the reverberation characteristics to adjust to music, speech…

Announcer:

Now, this isn’t done from the side panels at all, it’s done from the ceiling, entirely?

Purcell:

Up above, in the ceiling.

Announcer:

I’ve seen that in the side panels in the theater, but not the ceiling.

Purcell:

Yes. In this hall the side panels are concrete.

Announcer:

This sounds a bit like a nuclear reactor, where you pull the rods out and… theatrical meltdown…

Beranek:

They had trouble with these panels in one hall, in a very bad way. Now they’re fixing them so they’re counterweighted and can’t get out of control. But, in the radio concert hall in Berlin, which is a radio center in Berlin for music played by the orchestra that’s there… I might, incidentally, say that it’s common for the government radio network employ an orchestra full time, in Germany, for example. There they had reflecting panels that could be raised and lowered by a kind of a chain link mechanism. These were square links that went around a toothed gear. When you would turn the gear, this chain would move the panels. Well, somebody went in there to do some repairs and they took out a portion of the chain, and just left it hooked over the two sets of gears. Somebody pushed the electricity, the gears ran around to the open place in the chains and the panels fell down on the orchestra, smashed some people and some instruments. It was quite a mess.

Purcell:

Let me draw another picture here, an interesting one. We all know that cubic volume is a function of the absorption characteristic of the audience and the ratio established the reverberation. Another way of changing the reverberation time is to change the cubic volume. A great proponent of that concept is one theater consultant named George Izenour. George worked on a project in San Jose, the San Jose Civic Auditorium, in which you have a 2,800-seat house, and the whole ceiling moves down to close off the upper balcony, so that it becomes a 1,400-seat house, etc. That hall was open for about two and a half months, when the ceiling came down onto the seats. The building sat there for three years, in litigation. There was no audience present fortunately — nobody there. But the whole ceiling collapsed and fell. So, I’m very cautious about changing cubic volumes; it’s much easier to change absorption.

Beranek:

The other near tragedy, talking about concert hall tragedies, was in the Milano Opera House, the La Scala. It was bombed in World War II, and they decided to rebuild it exactly the way it was before. In fact, I talked with the architect after it was finished (I was in the same box with him, we went to an opera together), and he said, “We used no nails in it. We did everything by tying leather thongs, to make it just the way it was originally.” About two years ago, an audience went home after an opera, about 10:30; about 12:00 the whole ceiling fell down; all over the seats. Nobody was in it.

Purcell:

Are you familiar with the Ambassador Auditorium?

Beranek:

No… Where is it?

Purcell:

Ambassador College.

Announcer:

It has an adjustable acoustic…

Purcell:

Yes, that was a Bolt, Beranek & Newman project. I worked on that project with Daniel Mendenhall. I was the prime consultant on that project.

Announcer:

I’m not sure what’s up above that grill. I thought it was…

Purcell:

Curtains. Curtains are up above it.

Announcer:

Isn’t that one of the finest halls?

Purcell:

It certainly has a very nice reputation, I must say.

Beranek:

It does indeed.

Announcer:

Even though it only holds 1,200?

Purcell:

I believe it’s closer to 1,400.

Announcer:

Mr. Beranek, you mentioned earlier that on your first foray in this field, you found out that Sabin’s formula was wrong. How was it wrong?

Beranek:

This gets back to that seating problem. See, what happened… Sabin determined seating absorption in a hall at Harvard, in the large lecture hall of the Jefferson Physical Laboratory, they didn’t have seats. Students sat on wooden benches; that is, they had a wooden bottom, and they had cane woven back. Each bench would hold about four people. The students weren’t that big in those days, either. And, students tend to run thinner than older people, so there were a large number per hundred square feet floor space. Sabine calculated the expected reverberation time for the Boston Symphony Hall. Instead of figuring it out on the basis of area of the people, he assumed the sound absorption was based on the number of people. But, in Symphony Hall, the audience was spread out in bigger seats. So, he had expected to get a reverberation time of over two seconds, and with a full audience, he ended up with 1.8 seconds instead, and the difference is exactly in the amount of added area for that many people. Of course, that’s way back. But, you see, the thing that saved him was he used the same formula and the same seat calculation for all three halls he was intercom paring the new hall, the old Boston Music Hall and the Gewandhaus. So, since he made the same mistake in all calculations for all three, they were intercom parable. So, he came out safe; what he missed on was the absolute numbers.

Purcell:

He treated what he thought was a fact as an artifact — as a matter of fact.

Announcer:

Speaking of seating, another thing nobody seems to mention. If I remember correctly, in Symphony Hall in Boston, so they can clear the floor for the Pops, there are leather type folding seats, that are not uncomfortable but they’re on runners, and I think the absorption characteristic is quite different from regular theatrical seating now, they’re curved and padded.

Beranek:

You’re absolutely right. To get straight on how it’s built. The seats are in groups about ten feet long. How many is that, in ten feet?

Purcell:

That’s about, five seats.

Beranek:

Five seats maybe, in a row, and they’re fastened down on common runners, on the bottom, so you can pick up five at a time. Then they have a hole in the floor with an elevator in the front part of the hall, and they bring the seats over, put them on the elevator, take them downstairs and store them. Then they’ve got to take the floor up too, because the floor is a false floor above the main floor which is flat. The false floor is raked up as you go toward the rear. It gets to be about seven feet high at the rear of the hall. The false floor comes up in sections; they take it up and poke it down in the hole too. Now, these seats, you say, are not heavily upholstered? Correct. They’re leather upholstered? When the hall is empty, it’s much more reverberant than when it’s full and the result… when they rehearse in there, the orchestra pulls up a big canvas curtain.

Purcell:

Tarpaulin?

Beranek:

Tarpaulin, almost… they pull up, and actually what they do is they lower ropes down and they carry the curtain in and lay it on the front part of the hall, hook onto it, turn the motors on and pull it up, so the orchestra is not looking into the hall, they’re looking against this tarpaulin, as they’re rehearsing. So, it’s a rehearsal curtain, is what they call it. Then, of course, when the concert’s on, they don’t have that there, obviously.

Purcell:

Would you tell us the value of the staggered seats, some wide, some narrower, and no two seats behind each other, they come in between, like Montreal…

Beranek:

Really purely visual. It does help, some on the sound, but the idea is if you’re sitting behind two people and you’re looking over their two shoulders, you see more than if they’re not sitting right in front of you. That’s the idea.

Purcell:

A lot, too, will depend on the rake of the seat. If it’s a shallow rake, then you put seating behind seating. There’s a tremendous attenuation of sound over an audience like that, so that…our ears are lined with our eyes, so what is good visually, I always advise a client, is also good acoustically, because you’re getting a line of hearing as well as a line of sight. You’re not just killing high-frequency sounds. The wave length, of up around two kilohertz or three kilohertz, where you get all piccolos and your flutes, sound, are up in that frequency region. The wave length is about six inches, and so are heads, so the heads are scattering sounds and blocking the sounds. So it’s all in the line of sight.

Purcell:

In our last five minutes, what would you like to talk about?

Beranek:

I see. What’s left? I guess I’d say this, nothing to do with sound or acoustics. I’ve always been very interested in the city, and I’ve put a lot of effort in being a good citizen in Boston. This has led me into various jobs. I’ve been chairman of the Boston Symphony; I’ve been active in other organizations, like the American Academy of Arts & Sciences, etc. In 1963, which was a long time ago, I joined with a group of nine other people to go after a license for a television station, and we got the license. It turned out we didn’t go on the air until 1972, so in 1971 I resigned from Bolt, Beranek & Newman to take the year to get the station ready. I was president and chief executive officer of Channel 5 an ABC affiliate, which at that time, had more audience, almost, than the other two affiliate stations put together. We built a very fine station and I stayed with it as president for eleven years. Then we sold it. We sold it to John Kluge at Metromedia. So, I had an interlude doing something else, working with creative people at a television station. We did more local programming than any other station in the US, and we had a station that the New York Times, in an article written about a year before we sold it, said “It was probably the best television station in the United States.” So that was my other life.

Purcell:

Dr. Beranek, I want to thank you very much for agreeing to come to Los Angeles, and on behalf of the Los Angeles section of the Audio-Engineering Society, I’d like to thank you for spending an afternoon with the L.A. section.

Beranek:

Well, you’re certainly very nice. Thank you.

Purcell:

This concludes the official portion of today’s session. We’re going to do a little cleanup and wrap-up then if you want to join us — we’d head up to the Rusty Pelican for dinner, which is at the intersection of the #210 and #134 freeways. Thank you all for coming.