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Oral History Transcript — Dr. Vern Knudsen

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Interview with Dr. Vern Knudsen
By Leo Delsasso with W. J. King
At University of California, Los Angeles
May 18, 1964

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Vern Knudsen; May 18, 1964

ABSTRACT: Family background; identification with and influence of mentor Harvey Fletcher; bachelor's degree; calling as a Mormon missionary in Chicago, graduate course in physics with Albert A. Michelson. Work on electronics and acoustics at Western Electric at the invitation of Fletcher; influence of the work of Hendrik Johannes van der Bijl and Harold D. Arnold. Resumption of graduate studies at University of Chicago in 1919 and recollection of his work there with Michelson and Robert Millikan; change of dissertation topic to investigation of a hearing problem using vacuum tube circuits. Research on the hearing of speech in 1929 at University of California-Southern Branch; commission by Metro-Goldwyn-Mayer Co. for design of sound stages; design of auditoriums and studios; work on measurement of sound absorption. Dean of graduate division at University of California at Los Angeles, problems during his administration in establishing degree programs; his tenure as Vice Chancellor and as Chancellor; political problems with the Right. Director of National Defense Research Committee during World War II; applications of acoustics to anti-submarine warfare at San Diego Underwater Sound Laboratory. Organization of the Acoustical Society of America (ASA), role of Wallace Waterfall. Comments on teaching and religion; activities since retirement, nonprofessional interests; recent research in wave acoustics./p>

Transcript

Delsasso:

Dr. Knudsen, your life and that of Dr. Harvey Fletcher have been so interrelated over many years that in spite of the slight duplication which may occur, I’m going to ask you a few of the same questions you put to him. You said that your father as a small boy walked the same trail alongside a covered wagon from the Missouri River, as did Dr. Fletcher’s, few years earlier. What do you recall hearing from your family about this trip, and how did this pioneer background influence your life?

Knudsen:

I’ve thought of it many times, especially when I traveled on the Union Pacific from Los Angeles to attend meetings in New York or the east. The Union Pacific follows that route, and I always looked out of the window from Ogden, Utah all the way to the Missouri River, which was the very route, or very close to the route, that my father and Dr. Fletcher's father followed many years ago. My father followed it eight years later than Dr. Harvey Fletcher's. One incident on that trek, that my father made with his parents on the way to Salt Lake City, happened at Echo, Utah, where the three-year-old sister of my father died and was buried. Father had made several later attempts to locate the grave but, of course, it could never be located.

Delsasso:

I recall Dr. Fletcher's picture of you as a small boy fishing with birds singing around you. When did you become conscious that Dr. Fletcher existed? And what were your early impressions of him?

Knudsen:

I knew the Fletcher family from my early youth. I am nearly ten years younger than Harvey Fletcher, and therefore I knew younger members of his family better than I knew Harvey. Ten years is quite a disparity; when I was five, he was fifteen. And so, there was very little occasion for us to meet. My own father was Bishop in Provo, Utah, and it may be that Harvey Fletcher learned something of my early youth through our common church association at that time. I first remember Harvey Fletcher, though, when he had just returned from the University of Chicago with his Ph.D. degree. He was professor of both physics and mathematics at the Brigham Young University where, as a freshman, I came under his tutelage. And I’ve been pretty much under his tutelage ever since then. I’ve tried to walk in his footsteps in more ways than one.

Delsasso:

I think perhaps it would be interesting for you to review a bit of your early schooling, particularly under Harvey Fletcher, but there may be earlier remarks you wish to include.

Knudsen:

Well, of course, all of us are interested in the very first beginnings of influences that later determined significant events in our lives, or significant courses that we pursue. These may be legendary, but my mother and my elder brothers said that I showed a disposition toward exact thinking and mathematical sciences as young as three, when my brother taught me to tell time. There were a number of things of that sort, such as counting and simple adding of numbers; stunts of that nature were brought out by my brothers and by my mother at a very early age. And I think by the time I was in the eighth grade I knew quite definitely that I wanted to pursue either engineering or mathematics, or some subject that would be closely related to mathematics.

Delsasso:

When did you first become interested in physics as such?

Knudsen:

I was very definitely a convert of Harvey Fletcher. As I say, until then it was really my ambition to be either an engineer or a mathematician, but Harvey Fletcher had — and he yet has, as he manifested here last week — the magical power of a master teacher. I’m only one of his students and most of his students you will find, excluding myself have attained considerable distinction in the world of physics or acoustics. The thing that influenced me more than anything else in Harvey Fletcher’s teaching was his permission to let me work alongside of him, when he was studying the Brownian movement with the oil-drop technique. When I first looked into the telescope, the equipment that Harvey Fletcher had put together, and saw these dancing oil droplets there, moving at different speeds, up and down in zig-zag courses because of the impact of molecules, and learned from him that it was possible in such experiments to calculate how many molecules there are in a cubic centimeter of air or any other gas, my conversion was complete; I knew I could be nothing else but a physicist after that experience.

Delsasso:

Did you follow him to the Western Electric Company, now the Bell Telephone Laboratories, just after you finished your training at the university in Utah?

Knudsen:

Well, just after receiving my Bachelor's degree in physics at the Brigham Young University, I did what many young Mormons do; I accepted call to go on a mission. And went to the wicked city of Chicago, where later I became Secretary of the Northern States Mission, and I had all the powers of a minister. When I was 21 years old I performed my first marriage ceremony. I reca1l that the bride was about 58 years old and the groom was 65, and when it came to the end of the ceremony, as I had been taught to do, I said, “you may kiss the bride.” He said, “I’ll do that when I get home.” So, that was an interlude. I didn’t spend all my time marrying people. I preached Mormonism from the street corners of Chicago, among other duties that I had during the two years I was there. But during the latter part of my mission I did something which I think was unprecedented for a Mormon missionary. I was in Chicago, and I knew that Michelson was giving a course in the electromagnetic theory of light, and I thought, well, I’m just going to steal time from my missionary duties and go over and take this course of Michelson's. So, my first graduate course in physics was at the time I was also a Mormon missionary in the windy city of Chicago.

Delsasso:

I’ve always hesitated to ask you just what you did during these two years as a Mormon missionary. I’m glad to see it on the record here.

Knudsen:

I must add one other thing, because really the reward of my Mormon missionary experiences was something that I’ve been grateful for throughout all my life. It was there that I met another missionary, a lady missionary by the name of Florence Telford, and Florence, as you know, later became my wife.

Delsasso:

And it seemed quite natural then that you should continue your graduate work at Chicago since this was where you were located, or did you move from there?

Knudsen:

For a period of two years I worked again very closely with Harvey Fletcher. Through his intercession, I was invited to join the research staff of the then Western Electric Research Laboratories, where I worked with him, and became acquainted with vacuum tubes. I was told I was going to work with vacuum tubes. I didn’t know what vacuum tubes were: I’d heard about vacuum cleaners and I thought it was something associated with a vacuum cleaner. But I very soon learned from reading the memoranda by H. J. Van der Bijl that this was going to be a new facet of my life. And I know of nothing that turned me toward electronics, and later to acoustics, like reading these memoranda that were for the private files of the Bell Telephone laboratories, then Western Electric Research laboratories. This was a new world.

King:

Would you care to make some comments on Van der Bijl? I understand that he went back to South Africa.

Knudsen:

That is right. Van der Bijl certainly contributed more to the fundamentals of electron physics and the development of the thermionic electron tube at the Bell Telephone laboratories than anyone else. And as was mentioned in my interview with Fletcher the other day,[1] Fletcher believes that his work had a very great influence on the people at General Electric, e.g., Langmuir, Howell and others, who took up the work on thermionic electron tubes at the General Electric Company. I do not know about the priority but I do know that Van der Bijl was the pioneer worker here at the Bell Telephone laboratories, and his first book entitled The Thermionic Vacuum Tube[2] really was the classical text for a long time in this field. And it was used, first of all, by Van der Bijl in a course in the summer session at the University of Chicago, where many of my colleagues learned many of the things I had learned before from the Van der Bijl memoranda.

King:

Who else was associated with the work on vacuum tubes at that time?

Knudsen:

Particularly, R.V. L. Hartley. He's known now as the Hartley circuit man; he has the patent on the Hartley circuit. And E. H. Colpitts, who holds a similar patent; and his name is still associated with the Colpitts type of vacuum tube oscillator. The Hartley circuit was one in which the coupling was effected by inductance and the Colpitts circuit was one in which the coupling between the plate circuit and the grid circuit was accomplished through capacitance. And during my days at the Western Electric Research Laboratories, I had the good fortune to work on calculating the frequency and conditions that determined whether a vacuum tube oscillator circuit would oscillate, and if it would oscillate, at what amplitude it oscillated. All this came as a result of the work that Hartley had done, particularly on the theory of the thermionic vacuum tube oscillator. And Leo Delsasso, here, will remember that I required my students in electrical measurements to calculate the frequencies and the conditions which are necessary for oscillation with the different types of oscillator circuits.

Delsasso:

Indeed, I do, and on one occasion, I remember two of your students, W. A. Munson and my brother Lewis, using butcher's paper to make the calculations; there were yards of them.

Knudsen:

Very long, tedious.

Delsasso:

During the First World War you were required to make some observations on a broken submarine cable. This always intrigued me; as you know, later you brought your enthusiasm for this research here and we tried it here in the desert. Would you mind telling us a bit about that project?

Knudsen:

Yes, that's a rather pleasant experience. This was during the last month of the war, October-November of 1918. The cable to which you refer was the St. Pierre cable that was broken off 1700 miles out from Cape Cod. Our base of operation was at Chatham, near the site where the only German projectile hit American soil during the war. It was shot by a German submarine and it was enclosed with a little fence, very much like you see in the cemetery. This projectile is buried not very far from the site of the laboratory or cable station where we were making measurements. We were making measurements principally because the transatlantic cables couldn't handle all the communications Woodrow Wilson was having with Lloyd George and others in Great Britain in the concluding months of the war. And we were trying to speed up these cables so that the messages could get over as fast as they needed them to. And we found that the speed of the sending of signals at that time was determined by interference from earth currents. With these earth currents there is a more or less stable steady potential, but superimposed upon that there is a variable potential that has a frequency of seven, ten, something like that, vibrations per second. And this was a barrier to any higher frequency transmission at that time. One of the experiments which we performed at that time, I shall always remember — I was a junior member, so I wasn't responsible for the idea. A man by the name of Harry Hitchcock suggested that we stretch out a single loop over the earth's surface there, and so we had four miles of single-conductor cable that we spread into a loop, a mile on a side. We compared the kind of fluctuations that we picked up with an amplifier, and this was an amplifier which in those days, 1918, really had some gain. It had about 100 decibels of gain, and those who work with modern amplifiers today will realize that that was a lot. We had a lot of nursing to do to get this amplifier to operate so that these very feeble signals on the cable, or the ones that were picked up by this loop of wire over the ground, could be registered on a siphon recorder, which is the normal instrument the telegrapher used for getting these signals. Well, the similarity between the signals that we picked up on the cable and those that were picked up by this loop spread out on the earth was so very close that there was no question that the main signals were associated with the earth’s magnetic flux. And you will recall, Dr. Delsasso, that you and some of our colleagues spent a Thanksgiving vacation out in the desert. We went out to 29 Palms, which we selected then because it was further from civilization and further from electric signals than any place we could find in Southern California. Today it’s a thriving community. But you will recall that we had amplifier troubles then and we were able to get the steady potential but we weren’t able to get our amplifier good enough to measure the alternating components that we had measured in Cape Cod on the 1700-mile segment of cable.

Delsasso:

I recall that it wasn’t all hard work up there; that you used to go to dances, and I hope you can feel free to record as much of these dances as is proper on this tape.

Knudsen:

Dr. King may wish to expunge this from the record, and I grant him privilege to expunge this or anything else. But we were in the little community of Orleans, Massachusetts. This was the nearest community to our station. I must add, first of all, as a tribute to the very fine cordiality of the New England people: we arrived with our truck one morning at daybreak, probably 5 o’clock in the morning, and one of the native women from nearby met us with a big pot of coffee and a whole platter of sandwiches. That was my first introduction to New England hospitality. But what I’m going to say is somewhat on the other side of the ledger. Orleans, Massachusetts, population 500, had one bathtub which we didn't see during the three months we were there. But, as you have alluded to one of my pastimes, we did go to the community dances, and it was quite evident how far the winter had progressed by the olfactory sense that we experienced in the dance hall. By December things got pretty bad.

Delsasso:

Then when did you terminate your work at Western Electric and come to Chicago? That was in the fall of 1919.

King:

I wonder if we could go back on that, to the work at Western Electric. Did you have any opportunity to come in contact with H.D. Arnold?

Knudsen:

Yes.

King:

What kind of person was Arnold?

Knudsen:

H.D. Arnold was a person everybody admired very much. He was among that group of early workers with Millikan on the oil-drop experiments and had been, I think, more or less recommended by Millikan to the Western Electric Research Laboratories as the man to head up that laboratory for the first time. He, in a very real sense, was the creator of the research laboratories which later became the Bell Telephone Laboratories. He was the first man I met at the Laboratories. I was recruited by Fletcher's boss, R.L. Jones, who came to interview me at Chicago. After we discussed the general technical aspects of my qualifications and the nature of the work that I might be asked to do, I was almost dumbfounded because he asked me how much salary I thought I should receive. Well, this was the first time I’d ever thought about how much I should ask for, but I thought, well, I’m going to ask for quite a bit. I said, “Well, I think I should get a hundred dollars a month." He said: That’s very modest. We’ll make it $25 a week, which figured out to a little more than I had asked for. So, you can imagine how pleased I was that on my first proposal at $100 a month, was actually given something like $106 a month, and six dollars meant a lot in those days. Well, now, Arnold was really the director of the Laboratories during the time I was there and for many years after, and I met him on many occasions after that. But it was he who told me, first of all, that I was going to work with vacuum tubes and I, frankly, kept quiet because I didn’t know what they were. I was amazed when I found out they were thermionic vacuum tubes and that you could amplify with them or that you could generate oscillations. These were utterly new things to me, and this again was an opening of a very significant door in my life.

Delsasso:

What kind of a personality was Arnold?

Knudsen:

He was a very strict disciplinarian. I think he was an excellent administrator. I must say everybody respected him, but he didn’t hesitate at all about correcting faults that he found in anybody. At one of the meetings of the Acoustical Society, one of the members of his staff was delivering a paper. Nobody could hear this man speak — this was before we used microphones, probably 1929 or some such time as that — and he was speaking in Arnold Auditorium, which is the auditorium at the Bell Telephone Laboratories, named after him, of course. And Arnold spoke up and said, "I expect the members of the staff of the Bell Telephone Laboratories to speak up so that they can be heard. Hereafter you speak so that you can be heard." And this was the manner in which he reproved one of his members. But technically he was certainly a very, very capable man and was responsible for the organization of the Bell Telephone Laboratories which became, indeed, one of the best laboratories in this country. We were greatly indebted to the Bell Telephone Laboratories in World War II, in part because it’s very fine organization and its fine staff made some contributions in the field in which I worked which were very, very significant; for example, in dealing with the anti-submarine warfare program.

Delsasso:

I know he terrified me in Chicago, the first paper I gave, by criticizing one of his own men, just as you can say, for not speaking up and presenting his paper openly in the meeting. Are there any more items we should discuss in Western Electric?

Knudsen:

do recall one lecture I heard Arnold deliver in Arnold Auditorium. The title was "Acoustical Facsimile," and it dealt, of course, with distortion less amplification and reproduction of sound. At that early date he discussed in a very masterful way — he was an excellent person in discourse — the elements that go into reproducing sound so that it is so good that it cannot be distinguished from the original. And later, as you know, he discussed stereophonic amplification, which Dr. Fletcher described in his interview.[3] This was a great step, and Arnold was anticipating some of these things working together at that time.

Delsasso:

Well, I’ve never been too clear just what you did first when you came to Chicago. You were not married at that time?

Knudsen:

No, I wasn’t. Well, I chose Chicago — we talked about these things at the Bell Laboratories a great deal. There was no question about where one should go to study physics at this time, in 1919. Michelson and Millikan were both at the University of Chicago. Michelson, having been the first to receive, I believe, a Nobel Prize in any field in this country and certainly the first in physics, made this the place to go at that time. Therefore, there was no question about choosing the place where I wanted to go, and I’m sure that Fletcher’s intercession with Millikan had a beneficial influence in my having been accepted at the University of Chicago. I was not married, as I said almost harshly, at the time. I was engaged to this young Mormon missionary that I spoke about a little earlier, and we were in constant communication. She had been released from her missionary duties only a month or two before I went to the University of Chicago. We were scheduled to be married in December, as soon as the first quarter was over at the University of Chicago. And I kept that part of my schedule.

Delsasso:

I know that your years there have always intrigued me, and I almost feel as though I had been present, sitting at the feet of these great teachers. I believe some indication of your reaction to the great people that you were in contact with should be put on the record: Michelson, Mi1likan, Gale.

Knudsen:

Yes. I think you named those in the order in which I would name them from the benefits that I derived from them. I would also add, as most University of Chicago physics students would at that time, the name of A. C. Lunn, who was strictly in the department of mathematics but spent more time I think with the graduate physics students than he did with the math students. He was very much interested in the work that was then going on by Schrodinger and De Broglie. When are electrons waves and vice versa? What is the relationship between these various phenomena? This was in a formative period when the Schrodinger equation was being developed, and Lunn was very close to understanding this relationship between waves and particles. They often said that these "wavicles" behaved like waves on Tuesdays, Thursdays and Saturdays and like particles on Mondays, Wednesdays and Fridays. And Lunn lectured to us very much on the possibility of these being two aspects of the same thing. He was very close to the understanding of this unity of waves and electrons which later was developed by others. But, first of all, I think Michelson had a more lasting influence on my life than any of these professors, and his own notes, as you know Del, were very useful in the formulating of my own course in mechanics of wave motion and sound. That was approximately the title of the course that Michelson gave, and I cribbed a great deal from Michelson in the first courses that I gave here. Michelson never used a textbook and I never used a textbook. This certainly was a custom I copied from him. Millikan, similarly, did not use a textbook in his courses, and that was one other reason I did not. From Michelson I learned the classical things in physics that he taught and taught superbly well: mechanics of wave motion and sound, electricity and magnetism, electromagnetic theory and physical optics. Those were the four courses. No one knew the sequence in which he would give them. You attended these lectures the first time, and if he gave the electromagnetic theory the last quarter and wanted to give it again for some reason this quarter, you learned the first day you appeared that this was the same course you had a quarter ago. And so, you would just absent yourself. But everybody took all these four courses. They were not required courses but everybody took them. They were essentially required courses because every member of the faculty might examine you when you came up for your doctoral examination and Michelson always asked questions that were from these four courses that he gave. And as many of his students will testify, he lectured two lectures a week and then a quiz, two lectures and a quiz; that was the routine, and the amount of ground he could cover in one lecture was amazing. I know on one occasion he covered the whole theory of transient and steady state electrical phenomena in circuits of resistance, capacitance and inductance. Most of the textbooks will spend maybe 50 pages covering that, and he covered the high points of all of it. And I remember a Jewish boy coming out of the classroom with me one day and saying: "By golly, he covered more ground today than we used to cover in a whole quarter!” And that was quite characteristic of Michelson's lectures. But his lectures were models of perfection in delivery, composition, everything you would want in a master teacher. He never began a sentence until he knew the end of the sentence. It seemed like he was talking very leisurely. He always began his course of lectures with instructions: “Now, don't take notes during the class. But as soon as the class is over, if possible write up your notes as fully as you know how." And everybody promptly got out their notebooks and scribbled as fast as they could, and then spent maybe as long as six or eight hours to write up each lecture in his notes. And he always arrived at the mountain peaks and you had to explore in between; this was a very fine way of learning. I’m sure the students of Michelson learned a great deal about how to derive equations by actually having to do many of the steps of the derivation themselves. Millikan, in contrast, would go through every step; it was crystal clear. Millikan gave no instructions about not using one’s notebook and everybody used a notebook and took lecture notes from Millikan. You had a very fine set of lecture notes at the end of the course. I know if I had taught kinetic theory of gases or electron physics or anything of that sort, I would have used Millikan's notes very much as I’d used Michelson's notes. But Millikan did not cover anywhere near as much ground, and he didn't do it anywhere nearly as elegantly as Michelson did. Gale was an altogether different kind of instructor. He was a big, burly fellow, rough of language. He collaborated with Millikan, you know, in writing this first textbook in physics, which was used in almost every high school in the country for the first course in physics. And the time I was there they were revising it, which meant that Gale had to do the routine work of revising it. Millikan was very busy with other things. And you'd hear Gale pursuing Millikan, looking around for him. Millikan was probably visiting one of his students in the laboratory, and Gale wouldn’t have found him, and you’d hear him about, “Rob, oh, Rob, Goddamn that Rob, you can never find him when you want him!" And so, everybody knew Gale that way. I know one graduate student in particular said: “You know, the first day I was in Ryerson Physical Laboratory, I heard this fellow profaning, going down the laboratory, and I thought, that's the fellow I want to work with.” Gale was working in spectroscopy and Millikan later worked in spectroscopy. But I don't think I’d better go into those details.

Delsasso:

But you did have a chance to see the wonderful ruling engines and all the fine spectroscopic equipment?

Knudsen:

Yes. I think I must make one other remark about Michelson. In Michelson's course in physical optics he, of course, described the Michelson interferometer, but you'd never know it was Michelson's interferometer unless you had learned of it from somebody else. He simply spoke about the principle of the interferometer and how it had been used to measure the velocity of light, but he didn’t say, "I participated in these measurements.” I’m not sure whether he mentioned Morley's name or not, but I know he didn't mention his own name in that capacity. And, I know, once someone was asking him about his measurements along the railroad tracks — this didn't come from Michelson but it was one of the apocryphal stories around Chicago. Someone passing when Michelson and Morley were set up for the Michelson-Morley experiment said, “What are you doing there?” Michelson said, “Oh, we're measuring the velocity of light.” He said, “Why are you doing that?” And Michelson replied, “Oh, it’s such good fun.”

Delsasso:

Well, I'm sure those were pleasant and exciting years.

Knudsen:

May I tell one more anecdote? It's similar to one that Fletcher told in the interview, of his inadvertently prompting Michelson on one occasion. You know there are always bright boys in a class who can't refrain from making some comment when the professor is stalled for a moment in some mathematical derivation, and he sees the next step or thinks he sees the next step. And this young fellow said, “Professor Michelson, if you do…” and he got that far, and Michelson turned to him and said, "Young man, if you'll leave me to my own resources, I think I can extricate myself from this difficulty.”

King:

Did Millikan ever mention his oil-drop experiments?

Knudsen:

Yes, oh, yes. I think he described them in great detail. I have my notes somewhere. It might be of interest to see just what is in those notes in connection with the discussion we had with Fletcher about the partnership of Millikan and Fletcher in the oil-drop experiments, both on the measurement of “e” and on the Brownian movement work. If I find anything, I will write to you about it. I'm quite sure I have the notebook somewhere.[4]

King:

I'd like to ask one more question about these men and then perhaps we should go on. Which of these three men, Gale, Michelson and Millikan, do you feel had the sounder physical intuition?

Knudsen:

Without question it was Michelson, to my mind. Everybody may not agree with that. Millikan and Michelson, I think, influenced the course of physics in my day more than any other two you could name, and Chicago was very fortunate to have both of them. They were so very, very different. Millikan was the organization man and attracted men to him. They worked with him and he worked with them — he worked with them, I think, in a very fine manner. Everybody felt they were very lucky to be permitted to work with Millikan on these problems. I know in my day, the three years I was there, more people came to Chicago because Millikan was there than for any other reason. But I think most of them would agree that when it comes to which had intuitively the greater imagination, the greater creativity, Michelson would very definitely be singled out.

Delsasso:

And then you obtained your Ph.D. degree from Chicago in 1922, summa cum.

Knudsen:

No, I beg your pardon. I wish it were. Fletcher's was summa cum — mine was magna cum.

Delsasso:

Ok. And then you came to UCLA, I think the circumstances under which you found out that a UCLA — or a Southern Branch as it was then called — existed are worth a word.

Knudsen:

I think I'd like to go back once more here to the selection of my dissertation subject. Although Michelson was head of the department of physics at that time, Millikan was chairman; they had both a head and a chairman, and the head was always the senior man. Millikan was much younger — we must remember that. You’ll recall that Fletcher indicated that Millikan was only an assistant professor in rank at the time he went there in 1908 or 1909. And Michelson was a great man; he was one of the great seven who were brought to the University of Chicago in 1893 when the institution opened, and brought in at a salary double that which was paid any of the other professors in the United States at that time. And that’s one way the University of Chicago got off to such a good start. But Millikan almost always assigned the subjects for doctoral dissertations, and naturally I wanted a subject to work on at a relatively early period of my days there. I was married and I wanted to get a problem that I knew I could complete in a reasonable length of time. And as was customary, I went to Millikan’s office. He had a little black book, maybe four inches long and two inches wide, in which he had written subjects for doctoral dissertations. He read off many of these. I remember one of them dealt with the determination of the threshold of olfactory sense, and he referred to how far dogs could smell various odors. He felt that the techniques of diffusion, which were being developed in physics and chemistry at that time, was a suitable subject to work on. This is one he tossed around. But the one he was most eager that I should work on was the contribution of the electrons to the specific heat of metals. This was a subject that two of my predecessors as graduate students at the University of Chicago had worked on and abandoned because they couldn’t make headway. It was a problem that both Einstein and Debye had done some theoretical work on, and even they had not got very far with it. I did not feel that this was a suitable subject for a young man. I was married then, we were expecting our first child, and felt I had to have a subject which I could be reasonably assured that could complete in the three-year period had set aside for my graduate work at the University of Chicago. And so, I did not accept his bidding at that time. Shortly after, Millikan went on a visit to Europe. He had been gone quite a while, and Gale was taking over his duties while he was away. I went to Gale and told him that I was not happy about working on this subject, but would like very much to work on a subject for which I had special training by reason of my two years at the Bell Telephone Laboratories; namely, the utilization of vacuum-tube circuits to investigate a problem of hearing. Gale seemed to approve heartily and said, “I’ll tell you what you do. You go to work on this problem, and get it so far along that by the time Rob comes back, he won’t have the heart to take you off from it.” And I remember when Millikan came back and visited my room, he gasped very much when he learned that I was working on the sensitivity of the ear to differences in frequency and intensity. And that was my doctoral dissertation. It had a very definite influence in turning me toward acoustics work in later years.

Delsasso:

I’m sorry. That's an important piece that I should have remembered.

Knudsen:

You asked why I came to UCLA. I regarded myself, in a sense, as on a leave of absence from the Bell Telephone Laboratories when I left there. They had wanted me to stay at the time and go on to the Bahamas in the fall, which involved a continuation of the work on earth currents which we had been doing up at Cape Cod. This was a suitable place to make these studies because of the electrical disturbances that would occur in the Bahamas in the fall of 1919, but I carried through with my ambition to go to Chicago. When I left New York Dr. Arnold spoke to me and said, "I hope you wi1l be interested in returning to the Laboratories after you get your degree. We believe that this will be a place that you would enjoy working in," Indeed I had enjoyed working there very much. It was there that I did this first research on the vacuum-tube oscillator. I not only did this theory, working out the conditions for frequency of oscillation and how the various circuit elements affect the amplitude of oscillation, but I, for the first time in my life, conducted some experimental research of my own on verifying these equations in the laboratory. And as a young man, that interested and fascinated me very much. I knew that the Bell Laboratories was an environment in which I could be happy, and I had every intention of going back there at the time I left. During the final half-year at the University of Chicago I received offers from a number of places, not so much because I was outstanding but it was a post-war era, after World War I, and there was a shortage of physicists. So, I had an offer to remain at the University of Chicago or to go to two or three other universities. And I also had an offer to go to the Bell Telephone Laboratories. I had come so close to accepting the invitation to return to the Bell Telephone Laboratories that I went down to the Western Electric plant in Hawthorne, near Chicago, and had my physical examination, which indicated that I was fit physically. But at that time, we also had an invitation to come to this new branch of the University of California. It was then called the Southern Branch and it was only a junior college. I talked things over with Gale, and Gale just couldn’t understand me; he thought I should stay at the University of Chicago. And his profane reply to me was, “My God, Knudsen, it’s only a junior college!” I’d been interviewed by the astronomer W.W. Campbell about coming here. He was then Vice President of the University and was personally recruiting for this new branch of the University of California. His remark to me at that time was, "Well, you know, the place ought never to develop into a great university, but nothing can stop it." And this was a rather prophetic remark that I heard at that time. And really the decision, which Mrs. Knudsen and I made together, was, based in part upon the poor health of our first child, Marilyn. She was then 19 months old; she was not walking, and we didn't feel it was quite fair to take her to the Bell Telephone Laboratories, or to stay in Chicago, when we had an opportunity to come to Los Angeles. My older sister lived here and she had told me about the attractive living conditions out here. So we accepted the position and came out here on the invitation of John Mead Adams, whom we both know very, very well. He was chairman of the department of physics at that time. So, I came here in the fall of 1922.

Delsasso:

And this is the first time that I met you. I remember my first job was to build one of these oscillators with the tubes that you supplied from the Bell Telephone Laboratories, and that it was built entirely out of wood add parts that we scraped together. I was as amazed as you were, I’m sure, when we first saw one of these things actually oscillate. This opened a new era to me.

Knudsen:

I might make a comment there. No one ever thought of getting a dime for research in those days. If you did research and needed equipment, you had to make the equipment with your own hands. You'd have to get the equipment parts in some way, and my association with the Bell Laboratories again was such that I could get vacuum tubes and units of that sort, which we assembled with our own hands and with the help of Dr. Delsasso and later his brother, in putting these things together.

King:

Did you make any piezo-electric oscillators at that time?

Knudsen:

No, I worked entirely with the thermionic vacuum tube oscillators.

Delsasso:

You came here in 1922, and you’ve mentioned on several occasions you were welcomed by John Mead Adams, a Harvard graduate in 1905 who had accepted the job of starting a physics department here, singlehandedly, with a few bricks, a few meter sticks, and three string balances which he bought himself. This is by way of background, to show what Dr. Knudsen was willing to come to. You were, as I remember, quite impressed with Dr. Adams but not with the space that you had available.

Knudsen:

Dr. Adams said, "Space I have not, but such as I have I give it to you." I shared it with two others. It was a cubbyhole under a stairway, a cubbyhole for a janitor, and three of us occupied that room. We were so cramped; we had the smallest desks I ever saw. We sat either in front of or behind them, and when anyone came in to interview us, one of us would actually have to go out to make room for the visitor to come in.

Delsasso:

But we did develop and the years went by and in 1932 you were made chairman of the department of physics. And during that period, ‘32 to ‘38, you not only did a great deal of research in acoustics but you also developed a very close-knit and hardworking department. I think you should say something about your start in research, what you had, the lack of space on the campus, and how you solved that problem.

Knudsen:

Well, I often size up that research with an equation: S=E=0. S represents the area of the research space, and S equals zero. And E represents the research equipment, and E equals zero. So we began here with no research space or equipment. But I was interested in room acoustics for two reasons: one, Professor Michelson had asked me to look into the acoustics of a high school auditorium in Chicago; it was in difficulty at that time. And coincident with that, the collected papers of Wallace C. Sabine, who was Hollis Professor of Physics and Mathematics at Harvard University, had just been published in the spring of 1922. The reading of this book by Wallace C. Sabine was a turning point in my life, and it was influenced I’m sure by Michelson, who knew I had read the book and had been working on an acoustical dissertation. Therefore, he thought of me when someone asked about whether there was anyone at the University of Chicago's physics department who could tell them something about this auditorium. Well, I went over and simply referred to some of the things I had read in Wallace C. Sabine. I had read the book the night before, and told them some of the things in the Wallace C. Sabine book. This was just about a week or two before I was leaving, and I was preparing for my doctoral examination, so it was just a very casual inspection. But the reading of the Sabine book very definitely convinced me that architectural acoustics was a subject that I was going to work in. I was deeply interested in it as a result of that book. So when I found the absence of research facilities on the campus at the University of California-Southern Branch, I went looking about for a substitute laboratory, and I found six of the world's worst auditoriums among the high schools of Los Angeles. They became our first acoustical laboratory, and we began an investigation on the hearing of speech in auditoriums. It was soon quite clear that one of the factors that affected the hearing of speech was, of course, the loudness of the speech. And we knew that Fletcher and others at the Bell Telephone Laboratories had worked out very definitely how high the intelligibility of speech is as a function of the loudness, and that it had to be something like 70 decibels above the threshold to reach its maximum value. We knew also that noise was a factor in how well you could understand speech. It’s a matter of signal to background noise ratio, and the greater the background noise, of course, the poorer you hear speech, and you just don't hear speech at all if the noise level is high enough. So, the first part of this investigation was begun with W.A. Munson, who later worked with Fletcher on the Fletcher-Munson equal loudness level curve. He was a student in physics at UCLA at that time not than a sophomore; UCLA was only a junior college. He was my research assistant on that subject, and we investigated the effect of noise on the hearing of speech, simply by feeding a noise into the ears of a listener in a room in which you called out speech sounds, the kind of speech sounds telephone engineers use for determining the intelligibility of speech. And so, this was one factor we could determine in the laboratory here, namely, how well you hear speech in different levels of noise. So, we got the noise-interference factor. Then we conducted speech-articulation tests in all of these six auditoriums around the city. Most of them were rectangular in shape, and they had different times of reverberation. And about that time, we were able to extend this investigation into the sound stages of Metro-Goldwyn-Mayer, the acoustical features of which I had designed for them. So we had ready access to conduct speech-articulation tests there.

King:

About what time was this that you began work at Metro-Goldwyn-Mayer?

Knudsen:

1928. We had been working on this hearing of speech in auditoriums, I think, two or three years at that time. We generally had to work in these auditoriums at night when it was quiet, because we wanted to have only reverberation as the interfering factor. We were working in rectangular rooms that were relatively free from echoes. And so, we had an equation that gave something like this: the speech articulation in a room, in percentage, is 96, because 96 is the highest percentage you can get under ideal conditions of loudness, no reverberations, no echo, no noise. This was information the telephone engineers had obtained at that time. So, we had to determine these reduction factors, reduction because of reverberation, reduction because of loudness, reduction because of noise. So, noise, reverberation and loudness became three of these factors, and shape was another one which we cou1dn’t investigate. But, we said, for rectangular rooms we'd just assume the shape reduction factor to be unity that won’t affect the results. But we were able to quantitatively determine just what the effect of noise is, what the effect of loudness is, and what the effect of reverberation is. And so, this study, which continued over several years, led to the culmination in 1929 of this paper, “The Hearing of Speech in Auditoriums,"[5] in which it was possible, I believe for the first time, to calculate how well you hear speech in any rectangular room when you know the reverberation time of the room, the noise that’s there, and the power output of the speaker. And as part of that investigation, we measured the acoustical power output of typical lecturers at the University of California, Los Angeles. We had a microphone planted in a lecture room, and our measuring apparatus was in an adjacent room. The professors didn’t know their speech powers were being measured. And we found to our great amazement, that the average acoustical power output of different speakers ranged — that is, of these professors in the University — from four microwatts to 152 microwatts. We predicted that the four-microwatt speaker couldn't possibly be heard in a large auditorium beyond the third or fourth row. And later we had an opportunity to check that. You will recall, Delsasso — we won’t mention names — but the four microwatter once gave an important lecture in our Royce Auditorium before we had amplification and nobody could hear him really. I think I missed the mark by one row. He was not heard beyond the second row. This was our first investigation of acoustics at UCLA and that, as you see, did not require any special apparatus except a noise-maker, which we used for this investigation on the effect of noise on the hearing of speech. And this was W. A. Munson's introduction to physiological acoustics, or hearing acoustics, on which he's worked the rest of his life.

Delsasso:

Just when did we begin to make measurements on acoustical materials? We couldn't do any of this on the old campus, but it seems to me there were facilities in some private industries about that time.

Knudsen:

Yes. A plastering firm by the name of Simpson — something and Simpson — was interested in acoustical plasters and built for our use a reverberation room on Central Avenue, Los Angeles; it was in the Negro section of Los Angeles. It wasn’t altogether a safe neighborhood, not because Negroes were there, but it was more or less a slum area of the city and we were always worried about our safety. The reverberation room was not a room inside of a room; therefore we had to conduct our work at night to be free from noise because reverberation was measured by ear and the room had to be quiet. We didn’t have sound meters but we could measure the electrical power into a loudspeaker and if you weren’t overloading it you assumed that the acoustical power was proportional to the electrical power input, which is a pretty valid relationship if you don’t overload the system. So, we had a room not quite as big as our present reverberation room, not even as big as the first reverberation room we had on this campus, which was 19 by 20 by 16 feet. This room was a little smaller than that, but it was made of 10-inch thick concrete and it was suitable for making reverberation measurements. Some of the first careful measurements we made on the absorptive properties of acoustical materials were made in that primitive laboratory. That was before the physics bui1ding on this campus was completed in 1929.

Delsasso:

Those were almost the first measurements made on acoustical materials. Did the Bureau of Standards have facilities then?

Knudsen:

No, the Bureau of Standards did not. They came almost at that time, perhaps a year or two later. But there was the Riverbank Laboratory outside of Chicago that had been built for Harvard’s Wallace C. Sabine and was in use certainly at that time by Wallace Sabine's nephew, Paul Sabine. Wallace C. Sabine died in 1918, while his laboratory was under construction. A Colonel Fabian had become interested in Wallace Sabine’s work in architectural acoustics and built the laboratory, which is still one of the best acoustical laboratories for determining absorptive properties and insulative properties of building materials and building structures. It’s at Geneva, Illinois, and it's called the Riverbank Laboratories. That was operating, Leo; it had been operating probably from 1920, and so it was just opening when we began our reverberation measurements.

Delsasso:

This was really the beginning. You had the facilities for making reverberation measurements so that you could calculate what sort of reverberation you had. This was one of the factors that you had to provide in the formula for calculating how well speech could be heard in auditoriums. And you then did quite a few jobs. I think the one with Metro-Goldwyn-Mayer deserves special attention because it seems to me this was the first of its kind.

Knudsen:

Yes, I believe it was. No one else was working in acoustics, I guess, in the entire West Coast at that time, and so I can't claim any great distinction. They turned to the only person who was interested in acoustics, or was doing any work in the field at that time, to help them with the design of the first sound stages. I was told by Mr. Louis B. Mayer that they wanted these stages so well insulated against noise that they could have gunfire in a western picture going on at one stage and a full symphony orchestra going on at an adjacent stage, and you must not hear any sound from one stage to the other; the two sound stage must be completely isolated acoustically. And so, we set up as our design criterion a room inside of a room with, the inner room treated to be as acoustically dead as you could make it, that is, as free as possible from reflection of sound. It was essentially an anechoic room, as we call them today, though not quite as effective as the standard anechoic room. But the design we worked out for Metro-Goldwyn-Mayer became quite standard, not only for Metro-Goldwyn-Mayer but for the other studios here and the main features of the design have been followed in many studios constructed in other parts of the world. So this became, I think, definite pattern for the design of future sound stages.

Delsasso:

Then we moved to this campus in 1929 and you had an opportunity to design for the first time a satisfactory reverberation room that was tailored to your needs, and you subsequently made a good many measurements of acoustical materials. But you ran into some difficulty in making repeated measurements of the same materials on certain days. This gave rise to a whole series of experiments, and I think the reporting of these in some detail is important.

Knudsen:

This work, Leo, began in the fall of 1929, as you know; you were closely associated with it yourself, and your brother Lewis was my research assistant at that time. We began our work in these new facilities — and they really were very fine facilities in those days compared with the E equals zero and S equals zero that we’d had only seven years before. The new laboratory facilities were really unmatched; no other university had facilities like ours to carryout research in architectural acoustics. The first job was to calibrate the reverberation room, and calibration in those days, as today, meant determining the rate of decay of sound in a room at different sound frequencies. The vibration room in general is used to measure the acoustical properties of materials, the absorptive properties specifically. You do that by measuring the rate of decay of sound in a room, first, when the room is empty, and then when it has a known amount of material which has the absorptive properties which you wish to determine. And by a simple process, with these two sets of reverberation measurements you can calculate the absorptive properties of the material under investigation. Well, calibration meant measuring the reverberation time at different frequencies, and the reverberation time was defined then, as now, as the time required for the decay of 60 decibels. In general, it was necessary to have the sound in the room so diffuse that the rate of decay was logarithmic throughout, and this required that the sound be diffuse. We made it diffuse by introducing a rotating paddle, a large, rotating paddle which gave multiple reflections in all directions and thus made the made the radiation of sound approximately what it should be, which gives the same probability of radiation in all directions. And that is a condition that we tried to fulfill. But in the course of our work, as you intimated, we accepted the classical theory of the sound absorption, or sound attenuation of sound in air. The theory had been worked out by such distinguished physicists as Kirchhoff, Stokes, and Rayleigh,[6] and it had been shown by these distinguished physicists that the absorption of sound, in the air depends simply upon the viscosity of the air and upon the heat conductivity. And when you calculate the effects of those two things you find, well, at frequencies up to 4,000 cycles a second, there isn't enough absorption in the air to worry about. Everybody assumed that it was practically zero in all the experiments that had been conducted on the measurement, of reverberation of audible sound in rooms. And I'm sure at that time no physicist would have anticipated that this or any other research would lead to molecular collisions as the explanation of the peculiar dependence of reverberation on the humidity of the air. I must explain these experiments a little more carefully. Our observation was that when the air is moist — as it often is here when the breezes come in from the ocean and the humidity may be 80 percent or so — on those days, at the highest frequency we were using, which was 4,096 cycles per second, the time required for the decay of 60 decibels, that is the reverberation time, was of the order of 4 seconds, sometimes a little more than 4 seconds. But when, in contrast, the humidity was as low as 14 percent — as it was on one occasion when the air blew in from the desert and the room has air that is of about the same humidity as the air outside — instead of four seconds the sound died away 60 decibels at the high frequency sound of 4,096 cycles, in two or two-and-a half seconds. And, this, you can be sure was very baffling: why should this take place? We assumed of course that Kirchhoff, Stokes and Rayleigh knew what they were doing, and that their theory was the gospel on sound attenuation in air. And we, therefore, said, “Well, something is happening to the boundaries of our room.” It was just unpainted concrete, so our first step was to paint it. That didn't seem to make any difference. So, we said, “Well, let's use some harder paint.” And so we put various coats of lacquer and a very, very dense coat of enamel on it, but this didn’t make any difference. The weather still called the tune, and we were baffled by the vagaries of the weather, because it seemed that whenever there was a Santa Ana wind the reverberation time was down, and when there were breezes from the ocean, the reverberation time was up.

King:

How did you happen to notice the correlation between the weather and reverberation time?

Knudsen:

Everybody knows when there’s a Santa Ana wind here. You have a physiological reaction. In my case, my thumb skin cracks. Also, your nose is dry, you feel dry in your throat, and you observe electrical discharges from the ends of your fingers whenever you touch a conductor. So, you know when there’s a Santa Ana wind. The relative humidity is given every day in the newspapers. This last summer, for example, one day the newspapers recorded the relative humidity, reporting it was the lowest that had been recorded anywhere: it was reported as one percent. Now, we have never had it anything near that low; we had measurements only down to 14 percent. But it soon became evident that this wasn’t a surface effect, as certain acousticians suspected it was. Once, when in 1930 I attended some meetings in Budapest — it was a congress of architects — an engineer from Zurich said that he had the same trouble in his room. He lined it with bathroom tile and that, he said, corrected it. Well we thought about that for a while and found out that the tile treatment would cost $2,000, and we didn’t feel like asking for it. And then it occurred to me that we had the facilities here for a crucial test by which we could really determine whether the effect was due to boundaries of the room or to the air itself. It was at that time that I began to suspect the air. We had two rooms: one, 19 feet x 20 feet x 16 feet; the other was adjacent to it, constructed of the same 10-inch thick concrete, no windows, and a steel door, all the same as for the other room had, except this room was 8 x 8 x 9-1/2 feet. Now, in the small room you’ll have a certain number of reflections against the boundaries of the room per unit of time, whereas in the larger room the average distance sound travels between successive reflections is more than twice as great and so you’ll have fewer than half as many encounters against the boundaries of the room per unit of time. Therefore, the rate of decay of sound is going to be different in these two rooms, simply because the mean free path — as we called it then — the average distance sound travels between successive reflections is a function of the dimensions of the room. It’s strictly a function of the surface and the volume of the room, and approximately equal to four times the volume divided by its surface. If there is absorption in the air, then you must introduce a factor like you’d introduce for attenuation in any other medium; that is, if you’ve got sound propagated over a long distance, you’re going to have some sort of an exponential decay, as you do in electromagnetic waves and in every other kind of radiation. And so, I said, “This two-room experiment is the crucial thing. We'll measure the rate of decay in these two rooms" — and I wrote down the equations for the two rooms in which you have the exponential decay, which is continuous; the sound is traveling back and forth but the decay comes in as a continuous attenuation , an unknown which I labeled m. And also you have, of course, at each encounter against the boundaries of the room, reflection of, say about 96 percent of the sound intensity. And you have a succession of these 96 percent reflections. And so, you have two equations, one for each room, and one is the attenuation constant in the air, m and the other is the absorption coefficient of the boundaries of the room, x which is one minus the reflection coefficient. Now, as I said, if you have the temperature and the humidity the same in these two rooms, the air ought to be the same and, therefore, you ought to have the same attenuation factor m for the medium. And when we conducted the experiments in the two rooms, we found that the value of m was indeed a function of the temperature and the humidity, which we could reproduce time after time. And the absorption of the boundaries of the room didn't depend at all upon the humidity; we got the same absorption coefficient for the boundaries of the room, whether the humidity was 14 percent or 100 percent, whether the temperature was low or high. And, therefore, we had the first demonstration that this attenuation was in the air. It not only disagreed with the values that Stokes, Kirchhoff and Rayleigh had predicted on the basis of classical physics, based on viscosity and heat conductivity, but at the low humidities, around 14 to 18 percent, the attenuation which was a maximum at a certain humidity, was as much as 100 times the classical value that had been predicted by the Stokes-Kirchhoff-Rayleigh formulas and the maximum was propotional to the first power of the frequency, not the second power.

Delsasso:

This then led to a series of more careful examinations by the two-room method in not only the two concrete rooms, but in smaller steel chambers as well; this came along about 1932. You had the advantage of a young professor from Germany who had spent part of his time at Berkeley and came down here to work with you on the theoretica1 side, one Hans Kneser. It seems to me that the relationship between the experimental values that you obtained and the theory is now in order for discussion.

Knudsen:

I might take one step that leads up to this. In order to investigate the separate effects of the oxygen and nitrogen in the room, we abandoned the big room that I just talked about and we built two cubicle chambers, one six feet on an edge and the other two feet on an edge; both chambers had rotating paddles in them to make the sound field diffuse. These chambers gave us a ratio of three to one in the mean free paths. So, it was possible to work with oxygen alone, or with oxygen and water vapor, nitrogen alone, or nitrogen and water vapor. These experiments were well along at the time Kneser came to UCLA. I’m sure you can imagine our excitement — this was just before Kneser came—when we worked with oxygen alone instead of air, and we found that the maxima that occurred at humidity’s around 14 to 20 percent were just five times as large as they were in the air. It doesn't take very much intelligence to say, “Well, since there are five times as many oxygen molecules in oxygen as there are in air, this looks like oxygen might be suspicious.” So, you can imagine how we hastened to make our experiments with nitrogen. So, we filled the chamber with nitrogen; we observed no humidity effect whatever. As we added water vapor, we couldn't even detect any change in the rate of decay with our apparatus. It didn't change with temperature, and it didn't change with the addition of water vapor. Because the sound frequencies we used were audible and loud, you could hear the sound decay outside the chamber. It was a simple and convincing demonstration of how the decay rate depended on the humidity. We’d start out with perfectly dry oxygen and it would take, say, four seconds — this was in the six-foot cubicle chamber — for the sound to die away to inaudibility at a frequency of about 4000Hz. Then we’d admit a little water vapor, which we did simply by evaporating water into the chamber, and in a matter of a few seconds the reverberation would change from four seconds to less than two seconds and then down to almost one second, when the absorption was at its maximum. The change was dramatic because perfectly dry oxygen is more “transparent” than any mixture of water vapor with oxygen. We found also that the air or oxygen absorption increased with the temperature — approximately doubling as the temperature increased from 20oC to 55oC. The data we obtained established quite definitely that there was a reaction of some sort between oxygen and water vapor. This was the stage of our experiments at the time Kneser came here. He was a first-rate theoretical physicist and a good experimentalist as well. He had been trained in Marburg. His father had been professor of mathematics at Marburg, and he was here on a fellowship from a Rockefeller grant. He had spent a semester at Berkeley, and he spent the second semester here at Los Angeles, where he worked not only with me in acoustics but also with Professor Ellis in spectroscopy. He worked with me during the first three or four months of his visit. Only shortly before, he had worked with a theory that had been developed by Einstein for investigating the propagation of sound in a partially dissociating gas. Einstein had developed a theory which indicated that for one of the oxides of nitrogen which dissociates quite easily, there should be an excess attenuation of sound, and also a characteristic sound dispersion in this partially dissociating gas. And G.W. Pierce of Harvard had also found that carbon dioxide gas was highly absorptive at high frequencies. They were working mostly in the ultrasonic range, 30 kilocycles and up. And so, Kneser had this background with the Einstein equation and said, "Well, maybe this is associated in some way with the vibrational heat capacity of the oxygen molecule." And he went to work on that hunch and within a matter of a week or so; he had a beautiful theory that would account for our results. His theory predicted that the anomalous absorption we found was the result of an interaction between the oxygen and water vapor molecules. To use a simple analogy that Kneser used, when you compress a gas such as oxygen it probably can, by collision with other molecules, be set into vibration. So you have, say in a polyatomic gas, molecules in translation, in vibration, and in rotation. From spectroscopic data you know the heat capacity associated with at least some of the vibrational states. In the case of oxygen, this vibrational state can be excited at relatively low temperatures, even room temperature. By using the value for the vibrational heat capacity of oxygen, Kneser was able to explain our results by assuming that collisions between water-vapor molecules and oxygen molecules would be much more potent in exciting the oxygen molecule into the vibration than would oxygen-oxygen collisions. When such a gas is compressed the temperature goes up, which means the translational velocity goes up. And if it takes some time before a collision is energetic enough to bring about a transfer of a quantum of energy from the translational to the vibrational state, then there is a time lag between the condensation and the resulting pressure; that is, translational energy goes into vibrational energy. Consequently, the translation goes down and therefore the pressure also goes down. This time lag is proportional to the relaxation time, which is the average time required to bring about a cycle of these energy transfers. In the case of oxygen and water molecules, this time lag happens to include the periods of sound waves in the audible frequency range, and it is for this reason that collisions between oxygen and water vapor gave molecules these high attenuations associated with the vibrational heat capacity of oxygen. Kneser was thus able to account for our experimental results; there was only a difference of two or three percent, something like that, between our experimentally determined values of the maximum absorption and the values calculated by Kneser’s theory for both air and oxygen.

Delsasso:

And the report of this work, as I recall it, is in the Acoustical Society Journal in 1934. Somewhere there are companion papers, one by you and one by Kneser.

Knudsen:

Yes. I think it was ’33. I can tell you in a moment here; I have a reference to it. I know it's October — that I remember because I’ve referred to it so many times. Yes, Volume 5, 1933 and here's Kneser's article, the same Volume 5, pp.122-126. So, it's October, 1933, Volume 5, pp. 112-121 for my article, and Kneser’s article follows it. Mine deals with the experimental findings; Kneser’s, which is the companion article describes how this molecular collision process works. Some people questioned his interpretation and it was some time before his theory was generally accepted. Today I don’t think any competent acoustical physicist questions it, although as of 1964 there remain some unexplained discrepancies at high humidities.

Delsasso:

I think a word on the other gases that you used would be important for the record.

Knudsen:

In this Kneser also participated; we worked together in that spring of 1933. He came here in November or December of 1932, and we worked together, I think, until April or May. At that time he began working with Ellis, and he worked with Ellis through the summer. Kneser was much interested in the absorption of sound in gases, and together we explored many other gases besides oxygen and with many other impurities besides water vapor. Our first series of experiments consisted of working with other impurities besides water vapor, and we used various forms of alcohol, ether and other complicated molecules. Almost all of these affected the absorption the same way as water vapor does; namely, the effect of adding water vapor is to shift the frequency at which the absorption is a maximum to higher frequencies, that is, to shorten the relaxation time. And in the case of every other impurity we worked with, and we worked with maybe 15 or 20 altogether, the shift to higher frequencies at which the absorption was a maximum was a linear function of the amount of that impurity present. In the case of water vapor, it was more nearly a quadratic function, and in order to explain the action of water vapor, to explain the results we got, it was necessary to use this quadratic relation. The explanations of that are not yet fully know; there's still (1964) work to be done. Why water vapor collisions with oxygen should be different than the collisions between oxygen molecules and all other types we've investigated remains somewhat of a mystery. Some attempts at explanation have been made, but don't think they're satisfactory enough to introduce in this interview. We hope sometime even to work on that in the remaining years of our lives.

Delsasso:

And sometime shortly after this you reported this material to the American Association for the Advancement of Science, is that correct?

Knudsen:

I think that was in the winter meeting of 1934.

Delsasso:

This resulted in your being given the thousand-dollar Science Prize. I have '35 as a date for that.

Knudsen:

That's right. It really was New Year's Day, 1935. I didn't know anything about this. I had gone on to New York from Pittsburgh where the meetings had been held. I guess there were seven or eight hundred papers on the program altogether, and I didn't even know there was such a thing as an AAAS thousand-dollar prize. I was riding on a Pullman train in Wyoming at the time, in the lounge car. Prof. R. A. Millikan was on the train also, but he was not in the lounge car. I remember there was a good-looking dame sitting beside me reading a Denver newspaper. There were headlines, “California Physicist Wins Triple-A Prize,” and my photograph was there. They'd tried to reach me by telephone in New York but hadn't found me, so I read about this as I was on this Pullman train. I nudged this girl and said, "Look at this!" "What about that?" she said. I said, "I'm the guy!" I found Dr. Millikan a little later and told him. He was very cordial and nice about the whole thing. So, this was one of the great surprises of my life.

Delsasso:

Well, at that time you were chairman of the physics department, and remained so until 1938.

Knudsen:

‘32 to ‘38.

Delsasso:

Then the graduate work on this campus had made a start, and you were made the first Dean of the Graduate Division. You held that position for some 24 years, as I remember it, from ‘34 to ‘58. I think we should perhaps then shift to your experience there and your broader view of the overall university needs in higher education. I’m just going to ask you to reminisce a bit over those years.

Knudsen:

Well, the Southern Branch of the University, which now is UCLA, came into existence, as Dr. Delsasso well knows — he was a student at that time — in 1919. The University of California took over what was then the State Normal School here, and we became the Southern Branch of the University of California. As I’ve indicated, I gave my first two years in the junior college of this branch; in my third year, the third year of college was added, and the following year the fourth year. I think that’s the sequence, Leo.

Delsasso:

Wasn’t there an intervening two years — 1919 and 1920 — in which it was just a Junior College? And then there were two years in between before the third and fourth years were added?

Knudsen:

You may be right. Well, in 1929, as I’ve indicated, we moved to this campus. I’d been on the old campus seven years. We had on the new campus these very fine facilities, where we were carrying on a very active program in research. In the early 1930’s there was real agitation for graduate work at UCLA. We were growing fast and we had a good campus and a good faculty at that time. Many people and forces were working toward this objective for graduate work; perhaps chief person was the chairman of the Board of Regents, Edward A. Dickson, who served as a Regent of the University 40-odd years and was chairman of the Board of Regents during the time we moved to this campus in 1929 and also at the time graduate work was authorized in 1933. But it was a real battle to get graduate work authorized here. Many people felt that there should be graduate work only at the parent institution at Berkeley, and there were plenty of people up there who felt that we should continue to be just an under-graduate college. Many of the private universities of California, Taxpayers’ Associations, and others were not altogether enthusiastic or cordial about the matter of graduate work being offered at the UCLA campus. But with all these forces working for higher education at UCLA, and with the facilities we had, graduate work here just couldn't be denied any longer. It was authorized by the Regents of the University to begin in the fall of 1933, and the Regents limited the enrollment that first year to 125. There was no dean the first year. The provost, Dr. Ernest Carroll Moore, acted as chairman of the Graduate Council. I was a member of the Council, so I was associated with the beginning of graduate work in that way during this first year. We all knew that a dean was going to be appointed the next year, and one of the great joys of my life was when President Sproul called me into his office late in 1933, or early in 1934, and told me that he was asking me, on the advice of the committee, with which he agreed, to become the Dean of the Graduate Division. I think I’ve said before, Leo — I don't mind having it on the record here — I don't know of any other job in my life that I’ve ever coveted, I don't know if I broke the Tenth Commandment or not, but I actually wanted to be dean of whatever it was that was going to initiate graduate work here. I didn't want to become chancellor; I didn't want to become vice chancellor. But this is one thing that really, I think, I had a desire to be. At any rate, I wasn't breaking the Tenth Commandment because there you covet something that already exists, your neighbor's wife, or your neighbor's man-servant, your neighbor’s maid-servant or your neighbor's ox or anything else that is your neighbor's. I believe that's the text, isn't it; if you remember the Tenth Commandment. So, I wasn't coveting anything that anybody else had, and I don't believe I used politics, did I Leo to get the job?

Delsasso:

You did not, I’m sure of that. But these 24 years saw growth from a handful of graduate students to, oh, what number, roughly, when you finished?

Knudsen:

Oh, 6,000 graduate students the last year I was Dean.

King:

What were some of the major problems that you had to face during that period?

Knudsen:

Well, you see, we’d grown up as a teachers college, then a junior college. The recruitment of faculty, many of whom had tenure, had been employed for a teachers college. The departments of art and music and mechanic arts were, at that time, the major departments on the old Vermont Avenue campus. When it was a Normal School these were the major departments, and the faculty was made up a great deal for that kind of school. Beginning in 1919 they began to recruit people with the idea that there would be a college of letters and science, which was authorized that year; a junior college, at first, and then, as I’ve described, these later junior and senior years were added and graduate work started. And so, the faculty had many members that were just not qualified to give graduate work. So we had to have a screening process whereby you could separate those that were qualified from those that were not. The Graduate Council, over which the Graduate Dean presided, was first of all a body for authorizing those who were qualified to give graduate work. That was not an easy problem because almost everybody felt he was qualified to do it. I would say that was the most difficult problem we had to deal with at that time. We had to deal also, of course, with building up the library, with building up the laboratory equipment, and with the recruiting of faculty members that were qualified to really do the kind of work that's required at the graduate level. A great emphasis on research had to take place at that time. These were some of the problems we had to deal with. We were helped a great deal I wish to say, by the Dean of the Graduate Division at Berkeley and our relations with him were very cordial— Dean Charles Lipman. He was a botanist, and considerably older and more experienced than I was. I learned a great deal from C. B. Lipman.

King:

How does one go about resolving these problems?

Knudsen:

Well, I guess in the end the matter of publication had more to do with determining who is qualified. This is an easy thing to work with and it's a yardstick that's used more than any other. And we had as our criteria: the man must have established himself, not only quantitatively but qualitatively, as an investigator of some merit in the field in which he was going to teach at the graduate level, and in the work he was going to direct in Doctoral dissertations, or Master's dissertations at first. The Doctor's degree was not authorized initially. That came in 1938. So, you see, we had five years in which we offered only the Master's degree, and during that time we were preparing for the Doctor's degree. We knew we would at some time do it, so that was our other problem: which departments shall offer the Doctor's degree? That loomed as one of our important problems. We were recruiting people who would be qualified to do work at the doctoral level, guiding dissertation work and so forth. Initially, we were a small graduate school and almost every problem was taken before the Graduate Council. My process of administration called for arguing the matter until there was unanimity of opinion, and almost every decision that was reached by the Graduate Council during my many years there was a unanimous decision. There were a few, of course, on language requirements and issues of that sort which seemed split down the middle, but on most basic problems we would really argue the thing out; when you get everything on the table, you'd be surprised how many times you can get a unanimous vote on a subject if it's been argued properly.

Delsasso:

As I recall it, the history department was one of the first, at any rate, to give the Doctor's degree. I’ve forgotten just where physics fell in there, but very shortly afterwards…

Knudsen:

There were four departments the first year: history, mathematics, English and either philosophy — oh, I don't know; those three and one other. A year later, we had students come from Berkeley to Los Angeles to do their Doctoral dissertations, and physics was authorized the second year.

King:

Well, you can determine whether an individual was capable of conducting work at the graduate level by his publications. How could you determine whether a department was capable of doing that?

Knudsen:

For this, again, we had a quantitative criterion: there must be at least two men, we said, in a department who qualify for this guiding of the Doctoral dissertations before we would recommend them for approval to offer the doctorate work. This was a simple criterion that we had at that time. And there must be library facilities and laboratory facilities to support that work. Many departments had to wait a long time for authorization because the library or laboratory faci1ities were lacking.

King:

There's some central organization which sets up the qualifications on the library facilities, isn't there?

Knudsen:

Yes, but our affiliation with Berkeley qualified us in respect of library facilities.

Delsasso:

We had a large library committee with many representatives on it that helped us build up our libraries.

Knudsen:

Our present chancellor (F. D. Murphy) has been very enthusiastic about the library, and we recently passed the two-million volume mark in our total library here and are working towards the third million now. Also, we have good departmental libraries spread around the campus. It's anticipated, ultimately, that 40 percent of the total student body will be graduate students. That will mean — excluding the Medical School, which is also on this campus — there will be 25,000 students here in the year ‘67. I believe that's the target date. There will be 2,500 medical students, with interns and residents and the other students who would be working in medicine and the health sciences altogether. So, 40 percent, or 10,000, of the non-medical students will be graduate students. The present planning of the campus has that objective for graduate work.

Delsasso:

Graduate work had just gotten well established in the department here when the war came along and both staff and students disappeared. I recall that you came down to San Diego as director of the National Defense Research Committee to work on problems of anti-submarine warfare. I've forgotten just when you got there. I think it was between '41 and '42 that you were down there, but I don't recall exactly.

Knudsen:

You asked me when I went to San Diego to become Director of Research at the Underwater Sound Laboratory there. It was in May of 1941. You had preceded me there, as I remember, by a few months; I believe you had come in January of 1941. This was a continuation of an association that had begun in 1922, so that we knew each other very well at that time. Dr. Delsasso was first a student when came to the Southern Branch of the University of California. He took my courses in electricity and magnetism and, I guess, on electron tube theory and in acoustics. He became interested in acoustics himself and very soon was doing acoustical research. He did his doctoral dissertation work at Cal Tech, but did it on a dissertation subject that he performed over here; I think most of the experimental work was done here. I was on his doctoral committee, I believe, and our association has continued ever since then. I would like the record to show that I would certainly not be where I am today in my research work if it had not been for Leo Delsasso. And scores of others who have done research at UCLA are very much in Leo Delsasso's debt. He wouldn't want me to say this, but his record of research is much more impressive in the work he has done for others unselfishly and very effectively; when it comes to devising experimental means for doing things, Delsasso is really a new genius, and many of us are greatly in his debt because of the help he has given in devising the equipment we used in these experiments. We’ve always worked together on many, many things. His brother was my assistant during the time we were doing this work on the absorption of sound in air and other gases, and Leo was always on the side, giving advice to us especially about the experimental procedures that we used in this work.

Delsasso:

Well, we’ve said something about going down to San Diego.

Knudsen:

Yes, I think my last reply was that I went there in May of 1941.

Delsasso:

And I think perhaps it would be interesting to say a word about the problem of recruiting people and how rapidly this was really done. It was, I thought, phenomenal the way you were able to get a large number of competent people to come in to work on this problem.

Knudsen:

That, of course, was the important task at that time. It was quite apparent that we were going to be involved in the war at that time. The German submarine was a real menace and shipping was disappearing from the Atlantic at an alarming rate. Only a few months later 25 percent of the ships that left our East Coast for Europe didn’t get there; the Germans got them with their submarines. They, I think, were successful in sinking all the oil tankers that came from a certain South American field. The tankers were destined for somewhere on the New Jersey Coast. The German submarines out there had intelligence about when these ships were leaving for the U.S. They’d go out and sink the ship they were directed to get and that was their days work. They’d spend the rest of the day watching the bathing beauties on the beaches of Florida. And that’s about what the anti-submarine situation was at that time. We just didn’t have adequate facilities. A committee named by the National Academy of Sciences, consisting of E. H. Colpitts of the Bell Telephone Laboratories; W. D. Coolidge of the General Electric Laboratory; Max Mason, then at Cal Tech; Louis Slichter of MIT who is with us at UCLA, and V. O. Knudsen, was charged to investigate the adequacy or inadequacy of the devices that the U.S. Navy had available to deal with the U-boat. The work of this committee had preceded my going to San Diego to head up the research activity that was to deal principally with the fundamentals of underwater sound. Someone from the Bell Laboratories was detailed to go to New London, which was to be more of a hardware laboratory, a devices laboratory. Later, T. Keith Glennan became the director of that laboratory, and right now I don't remember the name of the other man. I can see his face but can't unlock my brain to tell you his name right now. Our big job, as you've intimated, Leo, was to build up a laboratory and build it up fast. We had very fine help from one person particularly, Ernest O. Lawrence, of the Radiation Laboratory at Berkeley. He came down to San Diego on several occasions, spent time with us, suggested names and actually participated in formulating our research program. And some of the best men we recruited came immediately from the Berkeley Department of Physics: F.A. Jenkins and Ed McMillan, and several others. And I went to the departments of physics of the leading institutions along the Pacific Coast. We got Karl Van Dyke, who was with W.G. Cady at Wesleyan, and L.J. Sivian from the Bell Telephone Laboratories, who was one of the best men they had in acoustics. I think within a month or two we had 15 or 20 outstanding men: Carl Eyring of Brigham Young University, a brother-in-law of Harvey Fletcher, who had done some outstanding work in acoustics at the Bell Laboratories; John M. Adams of UCLA; Ralph Christiansen, Ph.D. from Berkeley, who was teaching then at San Mateo Junior College; and others from Reed College, the University of Washington, and other places were outstanding physicists or engineers. Perhaps the most important one of all is still with us: Carl Eckart from the University of Chicago, who had been in thermodynamics and quantum theory and within a few weeks, was able to solve difficult problems in acoustics. P.S. Epstein and Harry Bateman of Cal Tech assisted us on a part-time basis, as did L.S. Jacobsen of Stanford University. These were distinguished men that came to our aid in those first months, and by November of that year, it seems to me, we had a first rate group of research workers and some fundamental R.W. Raitt and Ralph Christiansen were making experiments at sea. They discovered the deep scattering layer that has become a very important matter in marine biology. It is definitely associated with migrating organisms in the sea that move up and down diurnally and seasonally. This has been under investigation almost continuously by marine biologists since then. Many fundamental discoveries were made; then there were the early investigations of the soniferous animals of the sea; the croaker, the snapping shrimp, the porpoise and other sound producing creatures of the sea that have come so interesting. Many people from the Marine Laboratory, the Oceanographic Laboratory of the Scripps Institution, part of the University of California, were in on this work, Martin Johnson and others were responsible for the work on investigating the sounds made by the marine animals. Much work on the basic physics of the ocean has been going on ever since then such as the propagation of underwater sound, sound channels, reverberation, etc.

King:

Was this organization a basic research organization, or was it an applied research organization?

Delsasso:

Until the war actually started, it was predominantly of the basic research type. Then it began to be both applied and basic.

Knudsen:

I think Leo Delsasso could tell you more about these applied devices. Our original directive was that we were to be a physics laboratory to investigate fundamental principles. But when the war broke out, as Dr. Delsasso has indicated, the gadgetry became a more important part of our program and many of the findings were incorporated in sonar gear as the work developed, not only at New London, which was concerned principally with devices, but also at San Diego, which also became interested in devices. This work was coordinated from New York, where there was a committee of the OSRD, headed by John Tate and E. H. Colpitts. Much of my work following my year at San Diego was in the New York office and it involved an information exchange mission to England and Scotland. (May-July 1942) visits to other anti-submarine establishments and laboratories in Key West, Fort Lauderdale, New London, Harvard University, etc.; and collaborating in the preparation of three comprehensive reports: Survey of Underwater sound; Sounds of Surface Ships; Sounds of Submarines; ambient noise.

King:

Well, is it possible to say something specific about what you did? Are there still security wraps over this work?

Knudsen:

Most of the security wraps have been removed, particularly on my own work, which was concerned mostly with measurements of the natural sounds in the sea, those that are caused by waves and which are associated with the wind velocity and the state of the sea. We were able to establish definitely a correlation between the height of the wave from crest to trough and the amount of noise. It’s just as simple as impacts that come from the falling of a steel ball from different vertical heights above a steel plate. This was important finding in determining how much ambient underwater noise is generated as a result of the state of the sea; the noise varies greatly between a perfectly calm sea and a sea that is greatly perturbed. When the waves are 10, 20 or 50 feet high, the impact of this water hitting against the surface makes a terrific noise. And these things we correlated, so that if you knew the state of the sea, you could determine the amount of noise in the ocean. This, of course, was important for both listening gear and sonar gear as used on destroyers or submarines as well; it was especially relevant for detecting the noise from the propeller of enemy submarines. It was crucial in World War II in the role of the first successful acoustic torpedo, the M-24, which was a torpedo that had two hydrophones in its head. It was thus a listening homing device, essentially like a binaural pair of ears, and it could track the sound of a submarine’s propeller very much like a dog chasing a rabbit except it chased the noise of the propellers. The propellers were the main noise-makers. The Bell Laboratories, particularly, contributed toward the development of this device. My contribution was simply the preparation of tables based on the ambient noise in the sea (which could be predicted by observing the state of the sea) — the signal (propeller noise) had to be greater that the ambient noise or the M-24 torpedo wouldn’t take over. The tables gave the torpedo operators estimates of the effective range for different sea stats. This was a means of calculating how close to the submarine you must drop one of these acoustically-actuated torpedoes for it to take over. It mustn’t just chase the noise in the ocean; it must chase the noise of the propeller. And so, these tables were important in that respect. These tables were a simple but useful outgrowth of the writing projects on which I worked together with two engineers from the Bell Laboratories, J. W. Emling and R. S. Alford, in preparing the three comprehensive reports to which I referred. Although we participated in some of the measurements, most of the measurements and data were the work of others, the results of which we obtained from all possible sources. The data were carefully compiled, analyzed and treated in the process of getting the most probably values (Emling and Alford were experts in evaluating data) not only for the natural sounds of the sea that were caused by waves, rain and hail, but also by marine animals — the croaker and the snapping shrimp being the chief ones; and also the sounds of submarines and surface ships. The croaker especially affected the listening techniques because its sounds were of low frequency in the audible range; in contrast, the snapping shrimp made sounds in the high frequency range that sonar was using for echo detection. And so, the sounds from these two marine animals also became important in determining the range in which you could recognize echoes by sonar, or the range in which an acoustically-operated torpedo would take over when you were using it as a weapon. And so, you see, these three things: the natural sounds in the sea, the sounds that surface ships make, and the sounds that submarines make, were very important in our underwater warfare program. And in the case of the submarine, the noise of which comes from the propeller, it's largely a matter of cavitation. Cavitation is dependent upon the static pressures, say, at which cavitation bubbles explode. Cavitation is a function of how deep the submarine operates, and so, this again becomes a very important matter in developing tactics in an encounter between a surface ship that's after a submarine and a submarine itself. And the temperature gradient in the water is of prime importance, of course, in determining the path that the sound will take. If the vertical temperature gradient is great, as it often is in waters like that at Key West, where the surface temperature may be 74 to 76 degrees Fahrenheit and the bottom temperature is nearly freezing, the refraction is very, very great. The sound is refracted downward so much that a submarine cannot be detected by sound methods if it's a hundred feet deep at more than a hundred yards, or something like that, because the sound bends down so much by refraction. Well, these are some of the things that we were interested in, and my participation had more to do with these problems of noise than anything else.

Delsasso:

Well, perhaps that's enough on the wartime effort. Obviously, there was great success in some of these things, and you came back to the university — when?

Knudsen:

I came back in ‘44. It was quite clear at that time that the anti-submarine warfare against the U-boat would be successful. The acoustic torpedo had been developed and we were ahead of the Germans in that particular weapon. I was needed at the University, and I returned in the spring of ‘44, a year before the war was over.

Delsasso:

It was shortly after the war that we set up a course that was primarily designed to teach some of the Navy people about the underwater sound experiences gained during that time. Dr. Knudsen had a class of naval officers for several years there until the school at Monterey was completed and they took over this course.

Knudsen:

I should add that Dr. Delsasso had as much to do with that program as I did. It was a group activity. Delsasso had been in the Navy much longer than I'd been in research, and so it was the combination here that made that program as successful as it was.

Delsasso:

One thing we've missed is the discussion of the formation of the society that handles all of the acoustical work for this country, the Acoustical Society of America. I think a few words about the origin of that would be appropriate.

Knudsen:

I was discussing that with Dr. King a little earlier today, and Dr. King was especially interested in why the Acoustical Society was formed. I mentioned three things — I hadn't thought much about that, but I am sure they are the principal matters that affected the formation of the Acoustical Society in 1928, or '29.[7] The first of these was the increased interest in the applications of architectural acoustics, applications that involved the manufacture and sale of sound-absorptive materials, acoustical tiles as they are called today or acoustical plasters that use plastic materials. The work of Wallace C. Sabine didn't blossom fast or early. His work was done beginning around 1899, and it continued until his early death in 1918. He really sacrificed his life in war work in World War I. It was after World War I then that interest in acoustics began to be revived. F.R. Watson at the University of Illinois was working on this, perhaps, immediately after the war and was about the only investigator in this country. My dissertation for my Doctoral degree was in 1922, and I began work in architectural acoustics here at that time. Paul Sabine, who was the nephew of Wallace C. Sabine, was in charge of the Riverbank Acoustical Laboratory (at Geneva, Illinois) that had been built and equipped for Wallace C. Sabine, who died just before the laboratory was completed. The Bureau of Standards was becoming interested in making measurements of sound-absorptive materials at that time. We had planned our acoustical laboratory here and had conducted the investigation on the hearing of speech in auditoriums, to which we referred earlier today. Wallace Waterfall, who is presently Secretary of the American Institute of Physics, and has been Secretary of the Acoustical Society of America since its organization in 1929, was a pupil of F.R. Watson. He had obtained his Master's degree and was interested in architectural acoustics as a result of having worked with Professor Watson. Waterfall happened to be in Los Angeles at the same time F.R. Watson was in the summer of 1928. I invited Waterfall and Watson to have lunch with me at the Gables Beach Club, of which I had just become a member. I thought I had made a very fine investment because the original membership fee of $500 included lifetime dues. I figured I had maybe 40 or 50 years of life and $500 didn't seem very much to pay for both initiation and life dues. Well, the Beach Club lasted only a few days after we had this meeting, but it lasted long enough for us to have the meeting at which we decided there should be an organization known as the Acoustical Society of America. If I name the factors that were most important at that time, Dr. King, I would say that without someone like Wallace Waterfall to act as the catalytic agent to get these people functioning and reacting, we wouldn't have been able to form this society. But the three of us decided that Wallace Waterfall must get Bell Laboratories, and specifically Harvey Fletcher, in on this. Waterfall subsequently got in touch with Fletcher, who invited members to come to the Bell Telephone Laboratories, where the formal meeting was held at which we organized the Acoustical Society of America. The other factor that certainly loomed large and made the organization of the Acoustical Society take place at this time rather than earlier or later, was the advent of sound entering the world of motion pictures. I think I've spoken a little about that already. These, would say, were the most important influences. And, of course, the Bell Telephone Laboratories was the most important group of acoustical investigators in the country, probably in the world at that time.

King:

Now, why couldn't this organization find a proper place within the American Physical Society?

Knudsen:

That's a good question. There were not many people working in acoustics. I think most physicists felt that acoustics was a finished subject, that the work of Fresnel and especially the two volumes of Rayleigh[8] had more or 1ess written finis to acoustics. The idea prevailed that acoustics was a finished chapter in physics, very much as it did prior to the discoveries in electron physics, radioactivity nuclear physics and other things in 1895. At that time physicists felt the only thing that remained to be done was to improve the precision with which relevant measurements could be made. And so, where a paper was presented on acoustics at meetings of the Physical Society, prior to 1929, there was the general feeling: oh, this is old stuff; we don’t care for it. I probably had presented three or four papers at meetings of the American Physical Society. Fletcher and some of his colleagues I know had presented several and Watson had presented some. Also, G. W. Stewart and Paul Sabine had each presented one or more — this was about the extent of American researchers in the field of acoustics at that time. We were not able to evoke much discussion and there was a feeling that a society of our own would offer a more cordial atmosphere for discussion. Furthermore, the interest in acoustics included certainly the whole field of communications at that time: all the work that was going on in telephony, the recording of sound in the phonograph industry, the introduction of sound on motion pictures, work in musical acoustics, and in architectural acoustics which, I think, was the chief interest at that time — these matters were timely in connection with the organization, and were not of special interest to most other physicists. There were acoustical interests among physiologists, psychologists, musicians, architects, and otologists, and among workers in a number of other disciplines, such as telephone engineers, radio engineers, and recording engineers, all of whom were interested in acoustical problems. By bringing together these various disciplines we formed the Acoustical Society of America. So, it was a society in which disciplines that I've named were brought together (predominantly by physicists) and I think the events of the past thirty-five years are such that they indicate clearly that there was an interest in this subject, and a need for a new society of acousticians.

Delsasso:

I don't know just what the membership is now, but the meetings run about a thousand people at a session.

Knudsen:

I’m sure the membership is not over 2,000. I wouldn't guess; you'd have to get that number from the roster.

Delsasso:

Well, I note here that you were doing double duty to the extent that you were still Dean of the Graduate Division in 1958, and that you became Vice Chancellor in 1956. Am I right, that you were doing double duty during those times?

Knudsen:

Yes.

Delsasso:

You were Vice Chancellor from ‘56 until ‘59. Perhaps you would care to say something about those years.

Knudsen:

Well, they were years, of course, that interfered very much with research. It would be, I think, instructive to others but probably embarrassing to me, if you plotted the curve of my research activities as a function of time, from 1922 to, well, even to the present time. When I became Dean I said, “I’m not going to let my deaning interfere with my research. I’m going to be a professor as well as a Dean.” At first it was a little of deaning and much of professoring, and then it was about 50-50 between my duties of teaching and research and of deaning, and ultimately it became almost all administration. So, from 1956 on there was really nothing in my research record. If you looked at this curve, you would say, “Well, Knudsen’s hit zero line now so far as research is concerned” and this is almost true. I continued my interest in architectural acoustics, at least in reading about the subject and doing consulting work on a number of projects that interested me, but administrative duties more and more took up my complete time.

Delsasso:

And then in 1959 you were persuaded to become Chancellor of the University and this, I presume, added additional duties that prevented research. Would you care to say something about your years as chancellor?

Knudsen:

Yes. I think you may remember that at the 25th anniversary of the founding of the Acoustical Society I was asked to be a speaker, and I spoke about the irreversible process after one becomes a dean. Delsasso, himself, had been responsible for calling the deans on the carpet at this particular meeting, and there were four deans up there, (Harvey Fletcher, George Pegrum, Bruce Lindsay and I) all of whom had been very active in acoustical research. And I think there were four other deans up there who also were members of the Acoustical Society that could not be there. And the burden of my remarks that evening was to the effect that the process, once you become a dean, is irreversible. It's very much like the Second Law of Thermodynamics; you can advance to a vice chancellor, or a chancellor, or a president, or something of that sort, but you never become a physicist again. And I think the subsequent years more or less demonstrated that. This was a year or two before I became Vice Chancellor. I didn't know I was going to become Vice Chancellor; as a matter of fact, I didn't want to. I didn't want to become Chancellor. I admitted earlier today I wanted to become Dean of the Graduate Division. But I had had my fill of administrative work at that time, and I was interested in less rather than more administrative work. I don't look upon my career as a chancellor as a great contribution to the University of California. I did it because I felt I was obliged to do it. I'd been asked to do it and yet now I don’t regret it, because it did bring an experience that has enriched my life. And as I look back on it now, I don't think I would reverse the process even if I had the choice of doing so.

Delsasso:

Well, I'm sure it was done with great efficiency and with great benefit to the University as a whole, as well as to UCLA. You became emeritus and continued to spend many hours in your office. When you were Chancellor I'm certain you must have had the worries about personnel problems, and that sort of thing. But you have really proved that your Second Law is not quite true, for you have returned to doing research. I wonder if you would say a little bit about what you've been doing since retirement.

Knudsen:

Well, I thought first of all I was going to do some fishing. And I boasted to my many friends, "At long last I’m going to really spend at least four weeks one summer in fishing.” I think that during the first summer of my retirement five days were spent fishing. It was during the Democratic Convention that was held in Los Angeles in 1960, and I think after one or two days of fishing I became as much interested in listening to the wrangling that was going on at this convention. After five days I really had all the fishing I wanted in that year. There's been less time for fishing than I would like, but there has been time to do the things I’ve wanted to do and had not had an opportunity to do for a long time. I found myself more and more involved in extracurricular activities. I hadn't been out very long when I was in San Francisco, having what I thought was an earned vacation after a long career here, and I received a long-distance call and was told they wanted me to be President of the Hollywood Bowl. I’d been a Director of the Hollywood Bowl for 10 or 15 years. I said, "No, I’ve just retired from administrative work and I don't want any more of it." They said, "Well, this is the kind of administrative work to which you can't say no. This is a civic duty and you’re drafted, and this is something you have to take on.” So, I served a one year term as President of the Hollywood Bowl and another year as Chairman of the board of the Hollywood Bowl. And I got mixed up in more and more other extracurricular activities. I’ve long been interested in the California Institute for Cancer Research, which is an organization that sponsors research on the cancer field here at UCLA. I’d been Vice President of that organization, I guess, since its origin in 1948 or thereabouts, and I was persuaded to take on the Presidency of that about two years ago. That now occupies part of my time. I’m also interested in two musical organizations here in Los Angeles, the California Chamber Symphony Society of which I am Vice President and the Spring Music Festival, an international event for which I serve as a member of the advisory committee. So, these are some of the activities that I’ve had, but the most important activity since retirement is the revival of my interest in research. And I owe thanks to Delsasso and Dr. R.W. Leonard, who are working with me. We are now engaged in a project which we call "Wave Acoustics Applied to Architectural Acoustics," but it’s much broader than that. Its wave acoustics applied to all sorts of wave phenomena and it has applications to waves in water, waves in the earth, waves in the atmosphere, and waves in rooms. It just happens that our specific interest now deals with wave phenomena in rooms. This ties in, Dr. King, with the early work that referred to on resonance in small rooms, in which we demonstrated that reverberation was made up primarily of the free damped vibrations of the normal modes of vibration in that room. Much of architectural acoustics has been limited by the restrictions of ray or geometrical acoustics, which takes no account of the wave lengths of sound. To be sure, the dimensions you have in a room are of such a nature that you have to take into account the wave phenomena. And so, we began our investigation here with the reflection of sound from arrays of rectangular reflectors, panels that are similar to those that have been used in quite a number of auditoriums throughout the world, more in Europe than in this country, but notably in Lincoln Center Philharmonic Hall where these panels are used as reflectors. We have been investigating the diffraction of sound from such reflectors, and we’ve also examined the reflection of sound from the equivalent of ruled diffraction gratings, on which you have alternating transparent and reflective surface uniformly spaced. We expect to investigate both the reflected and the transmitted properties. We’ve done a pretty complete job on reflection from various rectangular arrays, and from single large panels as well as arrays of panels, and this data we reported at the latest meeting of the Acoustical Society of America.[9] We have two other projects that are in process at the present time. They will be followed by studies in three-dimensional models, in which we will have models of auditoriums that probably will be one half inch to the foot. We have one model under construction at the present time. Present investigations are concerned with the optimal shape and dimensions of enclosures for stages of multipurpose auditoriums to simulate a concert hall. That is, in this country especially, most concert halls are multi-purpose rooms having a proscenium. We are investigating the design of an enclosure, an acoustical shell — this is the general term — but particularly a music shell that will convert a multi-purpose auditorium that has a convention stage into a first-class concert hall. And we've been investigating the reflection and diffraction effects from different shapes, so that we get the proper division of sound between that which is reflected to the members of the orchestra or chorus, and that which is reflected to the audience. This is an investigation which is also in progress at the present time as part of this general investigation on the effect of wave acoustics on architectural acoustics. This will be a program that will continue for another two or three years, and Delsasso, Leonard and I are jointly carrying on this work. And so, I feel that an old-timer is being revived by two fellows who have been more active in the field than I have for a long time. I'm trying to reverse this law that I said was irreversible, and I'm having a lot of fun doing it.

King:

I wonder if you'd want to say something about some of your avocations. Is your interest in music a purely professional one?

Knudsen:

No, I've always enjoyed music. Harvey Fletcher referred in the dedicatory program here last Saturday to my first public appearance. When I graduated from the eighth grade, I played the clarinet solo; I remember it was Schumann's “Traumerei”. I wasn't an expert clarinetist by any mean, but my interest in the clarinet continued through college, and I made part of my way through college by playing with a dance orchestra in which I was the clarinetist. My father was a first-rate violinist and also a good clarinetist and much interested in music. Music was always a part of family life at home, and it's always been a very important part of my family life with my own children now. When our children were young, we had a trio made up of our three children, playing trios for violin and cello. The Knudsens are all very much interested in music. From the time we arrived in Los Angeles in 1922, we became interested in the Hollywood Bowl; it was the first year of existence of the Hollywood Bowl. So, my coming here was dated with that event and I, at once, became interested in the acoustical properties of the Bowl and have participated in such changes as have been made in the Bowl affecting its acoustics. So, there've been a number of musical interests along with my interests in architectural acoustics. The one other book I hope to write will be on the acoustics of music buildings. And the projects I'm involved in at the present time in a consulting capacity are very well directed toward that end; that is they deal with concert halls, opera houses, and multi-purpose theater-concert halls. And in another two or three years, together with the research Delsasso, Leonard and I are doing, I think it will be possible to write a book on the acoustics of music halls and music buildings, in which we apply these researches that we're doing on wave acoustics to these problems. There is also the consulting work I do: the Music Center downtown, the concert hall for Honolulu, one for Fresno, one for Wichita, and a music building for San Diego State College — these are some of the projects now that I shall hope to write up later in book or monograph form.

King:

Do you have any favorite composers or favorite forms of music?

Knudsen:

I’m very definitely committed to classical music rather than modern music. There's one possible exception and that, again, is a matter of association. I learned to appreciate Schoenberg's music because he was here for seven years, and I'd had along with my wife, some part in his coming here. We became very close colleagues here for departments as far apart as music and physics and we actually interchanged lectures. He spoke to my acoustics students on his art of music composition and I spoke to his composing students in his seminars on the acoustics of music rooms. So, it became natural for me to become interested in his music, and I especially became interested at the time he composed his Fourth String Quartet, which was to be played by the Kolisch quartet, one of the finest string quartets we’ve ever had in America. I listened to this quartet at rehearsals and at its performance and its phonograph recording — maybe 25 hours altogether. When you hear this very complicated music that many times, you begin to understand the beauty and the intricacy of it. It’s very much like a cathedral in its ornamentation and the ornamentation follows very definite laws, not only Schoenberg’s 12-tone row, but other techniques of composition, that correspond very much to those that an architect might use in designing an elaborate cathedral. And so, there is very much in the music of Schoenberg that requires a great deal of attention before you really appreciate it. There's much of his music I don't yet appreciate and don't understand, but Verklarte Nacht, the Fourth String Quartet, and his last opera, "Moses und Aaron" — these are three things that I am sure will endure possibly forever, in the repertoire of 20th century music. More and more they'll be appreciated by people who understand his music, and maybe 20, 30, or 40 years from now we won't think of Schoenberg in any other way except as a classical composer and a principal innovator of modern music.

King:

Let me ask this one general question. What do you think are the qualities that make up a good teacher?

Knudsen:

That's the most difficult question, I guess, that you’ve asked me. I think stated the other day that the three greatest teachers that live known in the field of physics were Michelson, Fletcher, and Kinsey;[10] I consider them outstanding. I spoke about Michelson a little this morning. Certainly, here was a great teacher, who was first of all a great research man, a man of extraordinary imagination and he had the distinction of being the first American to receive the Nobel Prize in Physics, a distinction he graced with becoming modesty. Unless a university teacher is active in research, he will usually fail to inspire students. There’s nothing, I think, in the preparation of a physics professor to take the place of research, and it must be important research, in order to inspire students. I don't think you can inspire students by proving, say, how high people can jump over an obstacle, showing that it follows the Gaussian curve, or some such thing. Some people do research that is not much more meaningful than that, and you can’t inspire students on that. But if you capture their imagination with your own research, I think you are likely to inspire them to go on in productive scholarship. If we’re speaking about teaching at the university level, I would say that's the greatest requirement of all. The second requirement is one that I’m sure I haven't exercised today, partly because I’m tired and probably a little emotionally disturbed because of the death of my sister yesterday. You must organize your material, and Michelson was the perfect example of the lecturer who was well organized. You could have taken a tape recording of anyone of Michelson's lectures that heard in the four courses I took under him, and I don’t believe you’d have to change a word; you knew where every comma would go. Every sentence would be a complete sentence. He had thought through the entire sentence before he began it. And sometimes you wondered, "Why is he hesitating?" He was formulating that sentence, it was to be an elegant sentence before he began it, and there was everything that should be in that sentence and nothing superfluous. Every word counted, and the ideas were succinct, intelligible and brilliant. And his presentation left much for the students to do in writing up his lectures. You couldn't help but learn and be inspired by that man, not only because he was a great research man but because he knew the English language and knew how to use it elegantly. He had elegance in his speech without any pretense of any sort at all, without any flamboyant character. It was good prose, so good that you could take it verbatim and print it, and it would be good even on the printed page, but like Einstein’s writing it required effortful reading — you had to fill in many gaps. The other requirement, of course, that is necessary is that you must know something about the learning process. You must know the subject matter, but it is necessary to introduce a little drama or excitement and to introduce something about what the subject matter is going to be used for. I know among my own students the one thing that live been commended about more than perhaps everything else is that, well, "Knudsen seems to appreciate that the punk sitting in the front row has to think about making a good living as well as making a good life." I think in some way in today's world you have to introduce the ideal and the practical in the proper proportions the academic and the applied in such a way that the students will feel that when they leave the university they not only know but they know how to do something. This has always been a characteristic of my life and I think I’ve had one foot in engineering and one in physics throughout my career. Such little success as I’ve had, I think, has been largely attributable to combining the practical with the theoretical. In all of my teachings, I have always said — Leo is a student of mine and I think he'll bear this out — that everything that is said in this course, or taught in this course, must satisfy these two criteria: it must be fundamentally important, and it must have some use either in discipline or in actual technological application. I've always found that by introducing technological examples of the principles you're talking about, there's an interest on the part of the student that you do not get otherwise. And so, I don't decry what the engineers are doing, what the technologists are doing; I think it is so closely associated with the work that we're doing in physics, that the physicist who recognizes also the technological applications of what he's talking about is more likely to inspire his students than the one who stays solely with the academic aspects of it. Those are my principal tenets of good teaching.

King:

Would you want to say a few words about religion? This is a rather private matter, maybe you would…

Knudsen:

I don't believe what I have to say is worth much and you can expunge or keep it as you wish. I was brought up under an orthodox disciplined religion, Mormonism, which some people think isn't Christianity. It is definitely Christianity. I think it is as Christian as any of the faiths I know. I wouldn't trade my training in this particular religion for any other I know of today. I think that the discipline I got in my youth, like the discipline that Harvey Fletcher got in his youth, had a lot to do with character building. I was an orthodox Mormon, I would say, quite definitely through my Ph.D. program, and as I said earlier today, I accepted a call to a Mormon mission. There was some skepticism at that time in my life, and I was a little uncertain at times about what I was doing, and whether it was what I should be doing. I know in my private prayers at that time, I prayed not to know whether what was doing was right, but I prayed that I would continue to do what was asked to do, at least so long as I was on the mission. So, there were elements of doubt about orthodoxy at that time; there's never been one doubt in my life about the religion of Jesus. The religion of Jesus has stayed with me throughout my life; the orthodox Gospel of Christ has been modified somewhat by my study of science by my association with other people in the university, by my reading, and by my analysis of things, and so orthodoxy didn't stay with me as it has stayed with many others who were brought up in the same faith in which I was brought up, or as it has stayed with others who have been brought up in the Catholic faith, the Protestant faith, or the Jewish faith. Some of them retain their orthodoxy throughout life. Mine is a different kind of religion now, and my religious activity today consists of listening to the Lord's Prayer, at one minute to six each morning, which I 've listened to now almost daily for fourteen years whenever I've been near a particular radio station. In the Los Angeles area its station KFAC, the music station which each morning, broadcasts a beautiful rendition of the mixed chorus singing the Lord's Prayer; so I always begin the day that way. On Sundays I continue to listen to the Salt Lake Tabernacle program of music and the spoken word. That is mostly musical, but it has a two-minute sermon and the sermon, as well as the music, continues to be important parts of my religious life. That is about the extent of my views on religion that I care to reveal today. I believe in religion, and I even believe in orthodox religion for youngsters. I don't believe it can persist beneficially beyond the time when you cannot reconcile it with other things, but I respect those who have more orthodoxy in their religious life than I have. I’m less orthodox than Dr. Fletcher, my esteemed teacher and friend and I certainly feel that he has good reason to continue in his orthodox faith. I feel that I couldn’t be honest with myself if I stayed with the same things I was taught in my youth, and so there have been some changes. But I shall always be grateful for the ethical and spiritual things that have made my life richer and better as a result of this training in my youth. I know it has had a great deal to do with my character formation and with my performance as a university teacher and administrator and for that reason I believe that religion has its important part in the world, a very important part, and it would be an unfortunate day, I think, for America if religion, even the orthodox part, should be thrown out. I believe it’s a necessary part of life.

King:

Dr. Delsasso, do you have any further questions?

Delsasso:

No, I think not. I think this sums it up. I’m sure there would be many items that we could spend time on, but I think these are the important things.

Knudsen:

I think I should apologize for not having been better prepared for today’s discussion. I’m afraid much of it is rambling instead of well organized.

King:

Well, have we left uncovered something we should have covered?

Knudsen:

Not to my knowledge.

King:

Dr. Knudsen’s sister passed away the day previous to the interview. The apology at the end of the interview is in reference to this loss in the family.

[1] Prof. Vern Knudsen interviewed Dr. Harvey Fletcher on May 15, 1964 for the Oral History Project of the American Institute of Physics

[2] McGraw-Hill, 1920

[3] Interview with Harvey Fletcher, conducted by Vern Knudsen for the Oral History Project of the American Institute of Physics

[4] There is no reference to the partnership

[5] Journal of the Acoustical Society of America, I, 1, pp. 56-82 (Nov., 1929)

[6] G. Kirchkoff, Vorlesungen uber mathmatische Physik: Mechanik (Leipsig, 1883). Gessammelte, Abhandlungen (Leipseg, 1882). J.W. Strutt, Baon Rayleigh, Theory of Sound, 2 vols. (London 1877-1896). Scientific Papers, 6 vols. (Cambridge, 1899-1920). G.G. Stokes, Mathematical and Physical Papers, 5 vols. (Cambridge, 1880-1905)

[7] Acoustical Society of America, founded 1929

[8] See footnote #6

[9] Journal Acoustical Society, 36, 2328-2333 (1964)

[10] R. Lee Kinsey, late Professor Physics at UCLA