Allan Pierce

Zierler:

Okay. This is David Zierler, oral historian for the American Institute of Physics. It is July 6th, 2021. I am so happy to be here with Professor Allan Pierce. Allan, it's great to see you. Thank you for joining me today.

Pierce:

Thank you for inviting me.

Zierler:

Allan, to start, would you please tell me your title and institutional affiliation?

Pierce:

Right now. I am more or less retired. However, I am associated with one particular temporary company, of which I'm the president. The company is the Cape Cod Institute for Science and Engineering and it is located in Sandwich, Massachusetts.

Zierler:

When did the Institute start?

Pierce:

Four years ago.

Zierler:

Was it your idea? Were you a founder?

Pierce:

Yes. The idea was that I wanted to apply for government grants from the United States Office of Naval Research. I wanted the cost to the Navy to be at very low overhead. This would have made the work less expensive to the government than if I had applied for a grant via my former university employer, which was Boston University. I had retired from Boston University in 2012 but I still had the option of applying for government grants via BU.

Zierler:

Allan, let's go all the way back to the beginning. Let's start first with your parents. Tell me about them.

Pierce:

Both of my parents were born in Clarinda, Iowa, a small town in southwest Iowa. They grew up there and were married there. It was the height of the depression, and my father’s first job beyond high school was with the Civilian Conservation Corps. (The Civilian Conservation Corps (CCC) was a voluntary public work relief program that operated from 1933 to 1942 in the United States for unemployed, unmarried men ages 18–25 and eventually expanded to ages 17–28.). The CCC was apparently relatively somewhat entranced with my father and offered to send him on a full scholarship to Purdue. My father, however, did not want to go to college with the stigma of coming from a poor family, especially as he would have to wear the CCC uniform all the time he was at Purdue. Possibly he was eager to get married to my mother at the time also. He turned the offer down. Somewhat later he took a job in in a small local factory (Lisle Corporation) and his job there was in the manufacturing of wind-chargers – devices that used wind-power to generate electrical energy for farms. In the process he began to learn the trade of being a machinist. I was born in Clarinda in December 1936 in my Grandmother’s house and I believe my parents lived with my Grandmother (who was a widow) for three years. They then moved to Columbus, Ohio, and my father worked in a company that made mining equipment. However, a job for a machinist opened up at Beech Aircraft in Wichita only three months later and my parents moved to Kansas and my father began work making military aircraft.

Zierler:

What was your father's field? What was his education?

Pierce:

He was a machinist. During World War II, he was highly trained by Beech Aircraft to do a variety of tasks involved with the manufacture of aircraft and the operation of a variety of machine tools. In those days, correspondence courses were very popular, and my father took many such courses. Several years after the war he became a civil servant and he then worked for the United States Navy, and this job was in New Mexico. Specific jobs with the U.S. civil service were then highly competitive and based on performance on civil service exams. My father was invariably a high scorer.

Zierler:

And what were the circumstances of moving to Kansas?

Pierce:

Well, we were all born in Iowa, but there weren't too many jobs. My father’s father at one time owned and operated two flour mills in Iowa, but these were a casualty of the depression. This was just before WWII and there certainly weren’t too many jobs for machinists in Iowa. So, we eventually moved to Kansas at the beginning of the war. There my father worked for Beech Aircraft Corporation, and he helped build airplanes, and when the war was over, he continued to work at Beech for a while, but in 1947 the family moved to New Mexico primarily because of my mother’s health problems. They wanted to live in a drier climate. My father worked at a couple of machinist jobs in Artesia and Hobbs, but landed a civil service job in 1948 at this big missile base (the White Sands Proving Grounds), and he was one of the early employees there.

Zierler:

Allan, in what year were you born?

Pierce:

1936. By the very end of it. The family was still living in Iowa at the time.

Zierler:

So you have pretty strong memories of the United States being at war during WWII?

Pierce:

Yes. I remember riding on trains with my mother and where most of the people on the trains were GI’s. Most of the young men were in uniform. My father was in a critical occupation and also had three children, so he was exempt from the draft.

Zierler:

Do you remember Pearl Harbor?

Pierce:

I was only three years old when that happened, and I do remember there had been a lot of flack about Japan and Germany.

Zierler:

And where did you grow up? Where did you spend most of your childhood?

Pierce:

Well, it was about half and half. Half was in Kansas, and the other half was in New Mexico. In Kansas, we lived for a couple of years in Augusta, and then several years in Wichita. Later we lived in New Mexico, first in Artesia, then in Las Cruces. My father worked at White Sands Missile Base, which was about 20 miles from Las Cruces. It was on the other side of a rather tall range of mountains, and the intervening land was owned by the government. For a couple of years my father’s job as head of the metal shops required that we live on the base. I rode a school bus to Las Cruces during that time.

Zierler:

And when did you start to get interested in science?

Pierce:

I guess I always was. And my childhood was during World War II and during the Cold War. And science was in the news a lot.

Zierler:

Did you tinker? Did you have radio sets or chemistry sets?

Pierce:

Yes. They weren't too much of a deal, but I did have a chemistry set and I messed around with it, and I did make my own crystal set—which were the type of radios kids would make in those days. I did make my own little radio.

Zierler:

Do you remember Sputnik? Was that a big deal for you?

Pierce:

Actually, Sputnik was launched in November 1957, just after I had started graduate school. I graduated from High School in May 1954, and then from New Mexico A&M in January 1957. I did not have funds to go to MIT in the middle of the school year, so I spent the next few months working at the College and then started at MIT in September 1957. I completed the four-year curriculum at New Mexico A&M in 2.5 years because I was in somewhat of a hurry. I wanted to go to school at MIT, but I and my parents didn’t have the money for me to go to MIT as an undergraduate. However, I knew I could get funding to go there as a graduate student, but I would have to begin there in the fall.

Zierler:

Where did you go for your undergraduate degree?

Pierce:

I went to the local college in my hometown: New Mexico A&M. They changed its name after I left to New Mexico State University. And it originally primarily taught engineering and agriculture. I had wanted to go to MIT, but my family could not afford to send me there, even with the possibility of a scholarship.

Zierler:

And what was your major? What did you study?

Pierce:

Physics.

Zierler:

Why physics? Why were you interested in physics?

Pierce:

I guess I was attracted to it, I had first thought of studying mechanical engineering. My father talked to a number of his engineering colleagues at the missile base where he worked (White Sands Proving Grounds), and they recommended physics for me. There was no real choice about going to New Mexico A&M (I lived at home and the tuition was very low) and the faculty of the physics department at New Mexico A&M was also substantially better qualified than the engineering faculty.

Zierler:

Were you attracted more to the theoretical side or the experimental side of physics?

Pierce:

I think I was attracted more to the theoretical side. It was all interesting, but the intellectual challenge of theoretical physics seemed greater.

Zierler:

And what kind of advice did you get about graduate programs to apply to?

Pierce:

I guess that one of the things was that when I was an undergraduate in physics, it seemed like almost all the physics textbooks were written by guys at MIT. So, I thought that the physics faculty there must be very good, so I went there. And I won a National Science Foundation Fellowship which allowed me to go anywhere I wished for free. Also, there was my professor (Richard H Duncan). I latched onto him when I was an undergraduate. He said, "This new book has just come out," well actually two books, "and we're going to look at it and read it." The book was Morse and Feshbach's Methods of Theoretical Physics. So, while I was still an undergraduate, I plowed through about the first half of those two volumes. I worked a lot of problems. Morse and Feshbach were professors at MIT, so graduate work at MIT seemed obvious.

Zierler:

And what area of physics were you most interested in pursuing for graduate school?

Pierce:

I really didn't know enough to decide at that time, but I had a disdain for stuff that consisted of what we called the "secret facts," where there was no real theory behind it. I liked the idea that physics stuck together. And I was interested in non-nuclear physics (which later became known as condensed matter physics). In my third year at MIT, Shell Oil Company wanted to give a fellowship to a graduate student who was definitely non-nuclear, and I was selected. I guess I was interested in theoretical physics of the non-nuclear type. But Shell definitely gave me the nudge.

Zierler:

What about acoustics? When did you start to get interested in acoustics?

Pierce:

Acoustics was relatively strong at MIT before WWII, but there were no basic courses in acoustics at the time I began as a graduate student. The principal professors had broken away from the Institute and started their own consulting firm (Bolt, Beranek, and Newman). I didn't know much about acoustics at the time. I did my doctoral thesis on atomic physics, molecular physics, quantum mechanics type stuff. The way I got into acoustics was because one of my professors (P. M. Morse) on my doctoral committee was on the board of directors of a company on the west coast called the RAND Corporation. RAND at that time was concerned with a variety of high-powered fundamental physics topics related to defense. They hired a variety of smart people with a good general background. When I first interviewed for the job, the physics department head, Albert Latter, said, “The last people we hired were from Harvard, students of Julian Schwinger. They didn't work out too well. So, we thought we'd try somebody from MIT.” And then I was hired. And, a few months later, after I first began work, he said, "We have this problem. And none of our current guys really want to work on it. It's a great problem for you." And so, he assigned me a problem. The problem had to do with how big were the Russian thermonuclear explosions. The Russian explosions were literally a really big thing, and we were trying to figure out all we could about them. And so, I was the kid that was supposed to figure out how big they were and study the waves they generated and so forth. All that seemed pretty interesting, and I got into it. Not strongly related to what I had done my doctoral thesis on, but something I was equipped to work on. You could say it was acoustics.

Zierler:

Would you say acoustics was a mature discipline when you were in graduate school?

Pierce:

I really don’t know. I don't know what you mean by "mature." There's probably a lot of things that most physicists still don’t understand about it. Some snobs will say yeah, it's mature. But they probably couldn’t solve the simplest acoustical problems.

Zierler:

What did you do after you defended your dissertation? What was your next opportunity?

Pierce:

I defended my thesis in October 1961 at MIT. And the next opportunity was the job at the RAND Corporation on the West Coast. That was a think-tank type place. The day I interviewed, I shook hands with Edward Teller. And they had all sorts of famous physicists coming in and out as consultants. They were tied in to the JASON group. A number of Cal Tech professors were consultants.

Zierler:

This must have been during the early years of the Vietnam War?

Pierce:

Kennedy became President in January 1961 before I finished my thesis in October 1961. Lots of things happened in short order. I don’t think there was too big an escalation in Vietnam until Kennedy was assassinated, in November 1963 (after I had left RAND). Most of the immediate concern with Rand at the time had to do with the possibility of an all-out nuclear war. This was the time of the Cuban missile crises.

Zierler:

Were you working on any defense-related projects for RAND?

Pierce:

That was the whole thing. The Air Force had established RAND as Project RAND in 1948 as a primary source of advice. There were lots of problems that they were working on at the time I joined the Physics Department. And I guess the Russians were working on such problems also. Over time, RAND assembled a unique corps or researchers, notable not only for their skills, but also for their commitment to interdisciplinary cooperation. It was the very height of the Cold War. There were a lot of problems as to what might happen if we did actually have a nuclear war. For example, what if electromagnetic pulses released during nuclear explosions disrupted radio communications.

Zierler:

Were you aware of the Acoustical Society of America at this point?

Pierce:

Well, not really. The RAND Corporation assigned me topics to work on and I started reading literature and thinking. A few of the works were classified, but much was in the open literature. I read a lot of papers in the Journal of the Acoustical Society of America. And I thought I should go to a meeting, start playing the science research game, and give a talk myself. And the first meeting I went to, that was in 1963, was a meeting of the Acoustical Society of America. It was in Seattle. I didn't know anybody there really, except that I recognized one of the professors, Uno Ingard, at MIT, who was active in the Acoustical Society. He didn't really know me because he didn't teach any courses I took, but we later became very good friends. The people at the ASA meeting were nice.

Zierler:

How long did you stay at RAND?

Pierce:

About two years.

Zierler:

Did you enjoy it? Was that a good experience?

Pierce:

I liked it very much. In retrospect, it may have been the best job I ever had. However, I was recently married and my wife missed Massachusetts. And so, she told me to go back to Massachusetts, and so I took a job in Massachusetts. I often reminisce about my leaving RAND, and dream about going back there.

Zierler:

And what was that job you took in Massachusetts?

Pierce:

It was a job with an aerospace company. The name of the company was Avco Space Systems Division and it was in Wilmington, Massachusetts. The new job wasn’t quite as exciting, although I was allowed to consult with Hans Bethe every so often.

Zierler:

And what was Avco's work?

Pierce:

I was in a research group that did a variety of tasks for NSF and the Air Force. Some of the projects that I personally worked on at Avco were similar to the work I did at RAND. The Air Force was very happy with what I did at RAND, so they gave Avco a (small) contract to do similar work. The funds came from the Air Force Cambridge Research Laboratories, which was at Hanscom Air Force Base in Massachusetts. The major portion of the work of the corporation was concerned with the first manned missile to the Moon, but I was not personally involved in that work.

Zierler:

Did you enjoy this work?

Pierce:

Not quite as much. It wasn't quite as elevated. But I was paid well, and I was in Massachusetts, which my wife liked.

Zierler:

Allan, did you feel like you were operating in a scholarly environment?

Pierce:

Yeah, I guess so. I did a lot of reading, spent a lot of time in various local libraries. I met some good people who were scholarly. Not as much as at RAND, but it was okay. While I was at Avco, I also taught graduate courses in the physics department at Northeastern University (at their Burlington campus).

Zierler:

How long did you stay there?

Pierce:

Three years. I got an invitation, out of the blue from the Mechanical Engineering Department at Berkeley to give a seminar. It seems the papers I had published at Avco had created some interest. At the time, Berkeley hinted that they were interested in hiring me.

Zierler:

What did you do next?

Pierce:

The Berkeley seminar got me to thinking about taking an academic job. However, I really didn’t want to move back to California. So, I applied to the Mechanical Engineering Department at MIT. They subsequently hired me as an assistant professor.

Zierler:

How did that opportunity come available to you, and was it difficult finding faculty jobs given that you were in non-academic appointments up until this point?

Pierce:

MIT wasn’t advertising for someone like me, and I recognized I would have to take a big pay cut if I left Avco. However, it turned out that the applied mechanics group in the ME Department was looking for someone who was strong in wave propagation, and I got very high recommendations. I think they were looking, at that time, for somebody who knew acoustics, who was good at it. And most of the research I had done previously had been published in scholarly journals like JASA.

Zierler:

What was your initial appointment at MIT? What kind of classes were you teaching?

Pierce:

Assistant professor, and I taught a graduate course on wave propagation. And I taught all sorts of theory about waves of all types. There were graduate students from mechanical, civil, ocean engineering, aeronautical, and geophysics. I taught basic courses in mechanics. solid mechanics, fluid mechanics, design, vibrations, materials science. I was promoted to Associate Professor after two years.

Zierler:

Now was the appointment related to the physics department? Did you have a dual affiliation there?

Pierce:

No, I was in the mechanical engineering department. My exposure to mechanical engineering subjects was very extensive. At that time, acoustics had more-or-less moved out of the physics department and was moving to engineering departments. The program at that time at MIT was jointly Aero, Naval Architecture, and Mechanical.

Zierler:

And were these considered natural homes for people with the specialty in acoustics?

Pierce:

At that time, yes.

Zierler:

Why do you think that would be the case? Why these branches of engineering.

Pierce:

Well, I'm not really sure, but acoustics is probably considered too classical to be regarded as pure physics. In more recent years, acoustics, at least the mechanics type of acoustics, has drifted over to mechanical engineering departments. Most of the recent acoustics-related books that you can buy are by people in engineering departments.

Zierler:

Did you take on graduate students?

Pierce:

Yes. The majority of the students in the MIT mechanical engineering department were graduate students, not undergraduates. I had MS and PhD students. I also had a number of BS students who were writing a BS thesis.

Zierler:

Allan, did you generally work on your own, or did you have collaborators?

Pierce:

About half and half. Most of this stuff was on my own. The general philosophy for the faculty at MIT was that they were supposed to bring in external sponsored research to cover half of their salary. They were also expected to support graduate students. In several cases, I took on part of a big project where another professor was doing another part. I was working on topics in medical ultrasonics, sonic booms, helicopter noise, lawnmower noise, diffraction by buildings, many other topics. Acoustics is a broad field. And I guess I didn’t have much in the way of supervision.

Zierler:

When did you first have the idea to write a major textbook on acoustics?

Pierce:

Well, very early in the game. But not too seriously. I wasn’t teaching acoustics as such while I was at MIT. Possibly a book on wave propagation - which is a major part of acoustics. A variety of professors taught different specialized topics in acoustics. Random vibration (Crandall), sound and structural vibrations (Junger), flow noise (Leehey), statistical energy analysis (Lyon), underwater sound (Dyer), wave propagation (Pierce), vibrations (Den Hartog), transportation noise (Lyon). Later, maybe five years after I started, Lyon began to teach a general broadly- based course in acoustics, and this was at the graduate level. I did, however, start to develop an acoustics course (with other faculty members) after I had left MIT and began to teach at Georgia Tech. I left MIT in April 1973 and joined the Mechanical Engineering Department at Georgia Tech as a full professor. Three years later I was promoted to the rank. of Regents’ Professor.

Zierler:

Was the idea that an acoustics course would be aimed more for undergraduates or graduate students?

Pierce:

At Georgia Tech, we had a three-quarter graduate sequence in acoustics. It was a sizable program. It is still quite strong today. I don’t believe we ever had an undergraduate course that was especially popular. The undergraduate curriculum was rather crowded.

Zierler:

Who would be pursuing a degree specifically in acoustics, or what disciplines would this be most relevant for?

Pierce:

Well, they could be almost in any discipline. I believe most of the graduate students taking more than one acoustics course were thinking in terms of a career that substantially involved acoustics. Many of the students I had in the wave propagation course at MIT were actually in the geophysics department at MIT. Because mechanical waves show up in a wide variety of disciplines, they are of very wide interest. A few of the students at Georgia Tech were in the physics department. But most of the students I taught at MIT and Georgia Tech were sort of in mechanics. Many years later on, I taught in a department that was solely concerned with acoustics. And that was at Penn State. They actually had a separate department for acoustics. All of their students were graduate students.

Zierler:

Allan, because the textbook is so important, I'd like to engage you chapter by chapter on some of the most important things that you wanted to get across.

Pierce:

Okay. I actually had several starts on the book. What sort of crystallized things was the receipt of a Humboldt Senior US Scientist Fellowship to work at the Max Planck Institute for Fluid Mechanics in Goettingen, Germany. This was in 1976 to 1977 and I began working on the book in earnest while in Germany. But I didn’t finish the book until 1981.

Zierler:

So we'll start right at the beginning in regard to the contents of the book.

Pierce:

I know that I finished the book back in 1981. That is a while ago. I do remember most of it. But I believe I worked on it for maybe seven years total, starting with the end of 1973.

Zierler:

But it's still in print, and it's been updated.

Pierce:

There are widely disparate philosophies as to what should be in a graduate level book on acoustics. I had my own opinions as to what should be in such a book. But, as it turned out, a large fraction of the researchers in acoustics agreed with me. I believe it is, and has been for quite a while, the widest-selling book on acoustics at the graduate level. I mean it sells better than most of the other currently available books. That doesn't mean it's the one most widely used as a textbook. But people, when they really want to learn something about acoustics, they read my book first.

Zierler:

Did you have any idea how successful it would be and how long it would be in print?

Pierce:

No. Well, I am familiar with books that have been a long time in print. Several books in other disciplines that I had used while I was a graduate student are still around. One was a book by a guy named Julius Adams Stratton, who wrote a book on electromagnetism. And I also remember one by Slater. Another on quantum mechanics by Schiff. And there is one on classical mechanics by Goldstein. Then there is one on statistical mechanics by Ter Haar, one on hydrodynamics by Horace Lamb, one on elasticity by A, E. H. Love, one on optics by Born and Wolf, a stellar series on the principles pf physics by Landau and Lifshitz. General Chemistry by Pauling, and Thermodynamics and Statistical Mechanics by A. H. Wilson.

Zierler:

Well, let's start at the beginning, Allan. First, tell me what is the wave theory of sound?

Pierce:

That's the title of the first chapter. The idea is that sound travels by way of waves. Not everybody believed things that way at the beginning. They thought maybe that sound consisted of little darts of little particles, but anyway, the wave theory goes back a ways. Not a long ways, actually, maybe only to the 1600’s. One of the originators was Isaac Newton. The idea is that sound waves are something like water waves which have ripples.

Zierler:

In what ways have experiments proved the wave theory of sound?

Pierce:

Well, many, many ways. The most common thing is that sound diffracts, which means sound can go around corners. When sound hits a corner, the energy can go partly in a different direction. And sound impinging from the air above on a water surface can excite ripples on the surface. Rather than just a bunch of little bullets, sound has to be some sort of disturbance traveling through a substance. This substance we call a “medium”.

Zierler:

In the second chapter, quantitative measures of sound. How do you quantify sound?

Pierce:

Well, that's actually a rather new thing that people started to do. You don’t actually see sound directly, although you can see its effects. Sound can cause objects to vibrate and you often can see these vibrations. About 100 years ago various scientists started inventing microphones and devices by which you measure quantitative effects of sound. The most common thing you sense is pressure, which is force per unit area. One senses pressure oscillations. You measure the amplitude of motions caused by pressure amplitudes and you work back from these to infer the amplitude of the pressure oscillations and these give what we interpret as the amplitude of the sound. Now-a-days, you can buy a device we call a sound-level meter. Such produces a number which is related to the time dependence of the local pressure in a sound wave.

Zierler:

Allan, what are plane waves and why did you focus on reflection, transmission, and excitation?

Pierce:

If an acoustic disturbance is constant along a planar surface, it is a plane wave. For example, if the disturbance is propagating in the x-direction, then it is independent of the y and z coordinates. If a disturbance is a plane wave, then it is relatively simple, although an idealization. If the disturbance changes directions abruptly then it reflects. If the disturbance continues to propagate in the same direction, then it is being transmitted. A plane wave is easy conceptually to excite.

Zierler:

How do we know that vibrating bodies have radiation and why is that important?

Pierce:

A vibrating body that is adjacent to a fluid causes the fluid to vibrate, and the fluid in turn causes adjacent layers of fluid to vibrate. We say that the disturbance propagates.

Zierler:

Why is it important to think about solid surfaces with radiation?

Pierce:

One can have air vibrate just by itself. But a solid surface is hard and can force the air to vibrate if the solid is vibrating. One general principle is that adjacent pieces of matter tend to move together. Thus, a sounding board on a guitar or a violin causes the adjacent air to move with it, and the disturbance then propagates out from the sounding board.

Zierler:

Why is room acoustics its own discrete area of research?

Pierce:

All of acoustics is an interconnected discipline. But room acoustics is the science of sound in rooms. To many of us, just how an acoustic disturbance sounds in a room can be very important. And of course, there's possibly a lot of money in designing a decent auditorium. You want music in a room to sound good and you want sound in theaters to be audible, the speech to be clear. This is how a lot of my colleagues actually make their living. You can possibly modify the configuration of a room to make it sound better.

Zierler:

You have a chapter on low frequency models of sound transmission, but not high frequency models. Why is that?

Pierce:

Actually, I do. When you ask the general theory of something, you begin by looking at the simpler cases.

One important quantity in regard to sound is the wavelength, which is ordinarily the sound speed divided by the frequency. The sound speed is something intrinsic to the medium, and the frequency is something intrinsic to the sound. Long wavelength sound is intrinsically low frequency sound, so long wavelength sound is ordinarily simpler sound. In later chapters, where I deal with shorter wavelength sound, I am dealing with higher frequency sound, and there are alternate approximate ways of looking at things. An example is to think of sound as travelling along rays. The main feature of sound is its frequency, and with that you have a wavelength, and the low frequency idealization generally has the wavelength as long compared to something else. Anything may be at low frequency. For high frequencies, then your wavelength is shorter. There's a big, big, big area of acoustics called ultrasound. Ultrasound just means short wavelength, and it's used a lot and it is very important. There's a huge industry called medical ultrasonics, where they use the sound in very short waves just to look inside the human body. They also use ultrasound to send messages.

There are several chapters that cover different aspects of high frequency acoustics. One of the things that works somewhat at high frequencies is what we call ray acoustics. The basic notion is similar to light traveling along rays. You have sound beams and these are sound traveling along rays. The rays are possibly curved. If the wavelengths were really short, the rays would stick together, but they wouldn’t necessarily travel straight. But at a low frequency, they wouldn’t travel together as rays so much. Instead, they would tend to spread out. This is a phenomenon we call "diffraction”.

Zierler:

Allan, what are ray acoustics?

Pierce:

Ray acoustics is an approximate theory of acoustics propagation. The sound travels along possibly curved lines in space. We say that the sound travels along rays. Thinking of sound traveling along sound rays is like thinking of light traveling along light rays.

Zierler:

But they're different than light rays.

Pierce:

Well, for one thing, light is electromagnetic, and sound is mechanical. But the mathematics is similar in the two cases.

Zierler:

What's an example of ray acoustics? How would I visualize it or think about it?

Pierce:

You think in terms of a beam, a possibly curved line along which acoustic energy flows. You might think oi the beam as being generated by a flashlight. Only this flashlight isn't generating light, it's generating sound, and the sound goes out into a beam. That's ray acoustics. And you obviously have examples where beams are shone out by devices on a ship, which sent out rays of sound.

Zierler:

Scattering and diffraction. Is that relevant for all kinds of acoustics, or a special area of acoustics?

Pierce:

Well, scattering means that the sound is not going to stay moving in the same direction. It moves in many different directions. And there's a lot of directions. Typically, the scattering occurs when a sound beam impinges on an object that is small compared to a wavelength. An example is where little particles are just floating around in air or water, and you shine sound at them. The sound may go out in all sorts of different directions, and there'll be scattered sound.

Zierler:

I'm interested in the area of viscosity and how viscosity would play a role in acoustics.

Pierce:

Viscosity is the process in which fluid motion tends to stick at solid surfaces. And it also causes fluid motion to tend to move together. The mathematical description goes back to George Gabriel Stokes, in the early 19th century. One of the most famous instances is the Millikan oil-drop experiment. It is a very famous experiment when small drops of oil were allowed to fall in air and the viscosity slowed down the particles. If the particle carried a charge, then the electrostatic force and the viscous force tend to balance each other out, and this enables one to measure the charge on the electron. It’s a very famous experiment and it got Robert Andrews Millikan (the founder of CalTech) a Nobel Prize. The experiment was actually done by a Millikan’s graduate student (Harvey Fletcher, who was the first President of the Acoustical Society of America). It got Millikan the Nobel Prize (1923) and Fletcher his Ph.D. In more recent years, viscosity is recognized as the principal cause of attenuation of sound in suspensions. Particles immersed in a fluid are vibrated back and forth by fluid friction during the passage of a sound wave, but the particles do not move perfectly with the fluid.

Zierler:

And finally, nonlinear effects in sound propagation. What's so important about the nonlinear effects?

Pierce:

Usually sound is of sufficiently low amplitude that it is a very good approximation to idealize the equations governing acoustic propagation as being linear. However, nonlinear terms are sometimes important. They change the frequency mixture and they distort the wave signature, causing higher frequencies to move faster than lower frequencies and for the amplitude versus time signature of the pulse to distort. The problem that I first worked on when I started at RAND was highly nonlinear. The Russians and the U. S. set off atomic bombs, and these gave rise to extremely high amplitude sound waves, and their waveforms didn't follow the usual propagation rules, and the propagation was very highly nonlinear. The waveform changed with propagation distance. There were a couple hundred thousand dead people in Japan in Hiroshima and Nagasaki, and those deaths are nonlinear effects. Radiation of nonlinear acoustic waves from blasts continues to be a big, big area of research now. A related area of research is the acoustically-induced backward force on small objects suspended in an inhomogeneous nonlinear sound beam. It's possible to shine a high amplitude beam on a small thing and actually get the thing to move backwards. And that's because the nonlinear effects sort of act together to make stuff move the wrong way. And that's a nonlinear effect. I don’t discuss this in my book. There didn’t seem to be room for all the interesting nonlinear effects I could have discussed.

Zierler:

Allan, how long did you stay at MIT?

Pierce:

I stayed about seven years. I started in September 1966 and left in April 1973

Zierler:

Did you achieve tenure at MIT?

Pierce:

No. I fully expected to be offered tenure and almost all of my colleagues expected me to. In those days, most junior faculty were not offered tenure, but I believe I was considered the best of those up for tenure at that time. I was never guaranteed tenure, and the process was not transparent. (None of the junior faculty in my group at the time received tenure. It was regarded as hard times for MIT. They did not need any more tenured faculty and the candidates who were US citizens would always be able to find another job. They could be easily replaced by less expensive non-tenured faculty if necessary.) The evaluation process extends a full year and goes through several committees, and many reference letters are solicited. There are no clear-cut criteria. I was told somewhat later that the College of Engineering Committee ranked me number one of all candidates that were up for tenure that year (1972). However, the very last tenure committee, the one chaired by the MIT President, turned me down. This Committee was the last in the sequence and had the final say. My division head, Stephen Crandall, was somewhat bewildered and told me I had done all the right things. He did some research and wrote letters asking various outside people of eminence as to my standing in my field. The verdict was that I was tied for number 1. He transmitted this to the upper administration and the reply that came back was “we never said he wasn’t a good man.” The department chair also wrote a letter of protest, but that did no good.

I was actually very confident of my own abilities, so being turned down for tenure did not phase me too much. I had lots of prestigious publications, a god track record for bringing in sponsored research, lots of friends in the external academic world, and a stellar reputation. I knew I could always get another position, and with a substantially higher salary. The Department threw a big dinner in my honor when I left and lots of nice things were said. I didn’t speculate too much as to what happened in the President’s committee. One of my senior colleagues told me it wouldn’t do any good.

The general opinion in the acoustical community, including professors at CalTech and the University of Toronto, was that “Allan Pierce was screwed.” Several opinions as to what happened were passed on to me by various senior faculty and what follows is my best guess as to what actually did happen. The times when all this occurred was when MIT was under fire because of the Vietnam war. Students were making noises because of the military-industrial-education complex. The Instrumentation Laboratory was picketed and subsequently divested (after which it became Draper Laboratories). The current president, Jerome Wiesner, was on a super black list of the then U.S. President, Richard Nixon. It was disclosed somewhat later that Charles Coulson had prepared a short list of 20 people regarding the Nixon administration on September 9, 1971 that came to be popularly known as “Nixon’s enemies list” and the list was expanded to include Wiesner. A White House memo contained a Nixon order to cut back on MIT’s subsidy in view of Wiesner’s anti-defense bias. Although I had not considered myself especially political, I had campaigned somewhat for Nixon, and had written a letter to the Globe that was anti-Lyndon Johnson. I and my wife were also paid guests to the second Nixon inauguration. My research background was connected to topics that were somewhat related to defense and manned spaceflight. One of my reference letters was written by Albert Latter, the head of the RAND Physics Department. Wiesner had served as Science Advisor during the Kennedy administration and had made statements that had established himself as an enemy of Latter.

Another theory was that Wiesner was strongly biased against acoustics as a research field because of events (involving money) that happened before Bolt and Beranek left MIT to start BBN. One of my senior colleagues told me that a member of the upper administration told him that “we told you that we are not going to tenure any one in that field again.” My guess is that Wiesner decided that, all other things being equal, he would not want to tenure anyone who might someday be on Nixon’s side in any squabble between Nixon and Wiesner. The explanation is, of course, not fully clear, and it is a long time ago. However, one strange thing that happened subsequently was that MIT invited me back only three years later. The ME Department had taken a poll and they decided that they wanted me back. I was of course flattered but I was then very entrenched at Georgia Tech. I had sponsored research projects ongoing, and I had junior faculty and graduate students working for me and depending on me. Also, Georgia Tech had just promoted me to the rather exalted rank of Regents’ Professor. So, I said no. That rather crazy chapter in my life was over. I stayed at Georgia Tech for 15 years and thrived quite well. I left in 1988 to take an endowed chair position at Penn State. As best I know, it was the only endowed chair in acoustics in the United States.

Zierler:

What was attractive about Georgia Tech for you?

Pierce:

It is a very good school. It was very much an engineering science school. Not a liberal arts school. The students were highly motivated and good. I liked the students and they worked hard.

Zierler:

Did you have collaborators at Georgia Tech? People you worked with there?

Pierce:

Yes. Actually, my reputation was then rather good and several outstanding people were attracted to Georgia Tech because I was there. The school acquired a considerable reputation as a research center in acoustics.

Zierler:

Such as who? Who were some of your key partners?

Pierce:

Among the faculty that came over the years and who worked with me were James Hadden, Jerry Ginsberg, Peter Rogers, Geoffrey Main, and Richard Salant. Hadden left somewhat later, Ginsberg and Rogers are now retired and are both rather famous in acoustics. Geoff Main is now a Department Chair at the Office of Naval Research. There is a biographical piece that Ginsberg and Rogers wrote about me in Acoustics Today. I often reminisce about the Georgia Tech days and regret having left there.

Zierler:

Where did you go next?

Pierce:

Penn State (Pennsylvania State University). I came there in 1988.

Zierler:

Were you recruited there?

Pierce:

Yes. The then Dean of Engineering, John Brighton, was instrumental in recruiting me. He was the former Department Chair at Georgia Tech. The circumstances that made the job attractive was that a very wealthy man, William Leonhard, a Penn State engineering alumnus and a relatively famous engineer had endowed a chair in engineering. Penn State had a graduate program in acoustics, and the University convinced Mr. Leonard to designate the chair as an endowed chair in acoustics. I regarded it as a very prestigious position. Pen State gave me a 25% raise at the time. I guess I had the only endowed chair in the college.

Zierler:

And was that in the physics department?

Pierce:

No. At the time I was recruited, the graduate program in acoustics was primarily a group of acoustics researchers in the PSU Applied Research Laboratory (ARL). For the most part, they each carried the honorific title of Research Professor. The Graduate Program wasn’t actually an academic department, and it had a Director (Jiri Tichy, at the time I was recruited) who reported to the Vice-President of Research. A number of faculty in the engineering departments and other departments, such as physics, had associations with the Graduate Program. Both the ARL-affiliated staff and the faculty from regular departments taught graduate courses. The Program goes back to 1965 and it was started in response to a desire expressed by the US Navy that people at advanced degree levels be trained in acoustics. It is the only graduate level degree program that offers a doctorate in acoustics. A substantial fraction of the ARL-IRAD (Independent Research and Development) funds was devoted to the support of graduate students in acoustics. My recruitment coincided with it being made an academic department. I was the first person to be given tenure in this department. I also received a quarter-time appointment in the mechanical engineering department. It was necessary for me to choose a second department and I chose ME, primarily because I was coming from an ME department.

Zierler:

Was that one of the rare standalone acoustic departments in the country?

Pierce:

The situation was rather unique, in that the administrative structure was not that of an academic department. However, it had the authority to give courses and to give graduate degrees. There was an analogous program at the University of Hartford, but it was only for undergraduates. Many of its graduates came to Penn State and enrolled in the Graduate Program in Acoustics.

Zierler:

Do you know how far back that goes? How far back acoustics departments were standalone?

Pierce:

It goes back to 1964. There is an article, “50th anniversary,” in Acoustics Today that discusses the history. The creation of the Graduate Program required a special vote of the graduate faculty, and many of the ARL employees (and there were many of them) had appointments as members the graduate faculty, and they were strongly in favor of the Graduate Program being created. I believe the program was under the auspices of the Vice President of research. It did not report to any of the college deans. As to its original instigation, I believe the start came from the U. S. Navy which did and sponsored a lot of work in acoustics. It was complaining that it was having a hard time getting people who were trained to work on acoustics. And so, the Penn State ARL stepped forward and started their own graduate program.

Zierler:

Allan, when did you start to get interested in acoustical oceanography?

Pierce:

I dabbled in it over the years, but I did research in many different facets of acoustics, and I didn’t do much substantial in acoustical oceanography until I came to Boston University. However, the person who nudged me the most in that direction was William Carey. It's an intrinsically interesting subject, but my earlier interests were sonic booms and structural acoustics and a number of other things. Sometime after I went to Boston University, Carey asked me to help him with some of his projects. Boston University was my last employer before I retired and I came there as a Department Head in 1993. The Department was woefully short handed and I was enabled to hire a number of new faculty, which for the most part turned out to be stellar appointments and who won major prizes. Bill Carey was one of the new appointees and he had some interests in underwater acoustics, which was alternately sometimes called acoustic oceanography. It had to do with the use of acoustics to study oceanography, or the use of oceanography to study acoustics. People were trying to understand what is going on in the ocean, and acoustics helps to understand that. It can be really important for the detection of mines. Bad guys tend to drop bad things down to the bottom of the ocean. You've got to be able to look at the bottom of the ocean to see what's there. And that is but one aspect of acoustical oceanography.

Zierler:

Allan, what about wind turbines? When did you start to focus on the acoustical implications of wind turbines?

Pierce:

My principal effort on wind turbine noise resulted in a POMA paper coauthored with a graduate student, Evangelia Kotsari. The paper was titled “Simplified Theory of Wind Turbine Noise.” I believe it was a fairly good paper, but I was not focused on wind turbine noise at the time. I was at Boston University and renewable energy was very topical. I had a very good PhD student, Amadou Thiam, originally from Senegal, and he wrote his thesis on ocean wave energy. The thesis was completed in 2014, but we had worked on the topic for maybe five years previously. For most of that time, Amadou was working at General Electric (supported by a Fellowship) and I was retired, working part-time out of the ASA Editorial Office on Cape Cod. Amadou would come and visit me one day a week, usually on Saturdays. Wind energy and ocean wave energy got to be a big deal about maybe 20 years ago. We knew that you could possibly generate energy from wind or ocean waves. I actually got first interested in the use of water waves to generate energy Amadou followed up with the study of an existing device (Pelamis from Scotland) that consisted of a connected set of linked cylinders on top of the ocean, and they flexed. Magnets were in the coupling between the individual cylinders. Partly-open loops of wire encircled the magnets. The process of electromagnetic induction set up an oscillating electric current in the wire encircling the magnets. Regarding wind turbine noise, the wind makes the air twist through the air in a shape like a screw. The problem with wind turbines, which bothered many people, is that they make some noise. So, the questions are, can you predict how much noise they make, and can you figure out how to reduce the noise, and those are the problems Kotsari was working on.

Zierler:

In your work on structural acoustics, what kind of structures did you focus on?

Pierce:

The work was mostly generic – no specific structures. The first work I and my colleagues did at Georgia Tech on this topic had to do with the radiation of sound from a structure where you knew the vibration all over the surface. Ideally, you should know both the displacement and the normal component of the velocity. However, you really needed to know only one. We succeeded to express the problem as a variational principle, and that was the starting point for fundamental studies. I worked on this problem with Jerry Ginsberg and with Sean Wu, a graduate student. The work was funded by the U. S. Office of Naval Research and they had a long-term interest in the radiation of sound by submarines and in the acoustic echoes from submarines. I believe, however, that the actual details might have been classified. The science involved, however, was of interest. One practical problem is that a submarine radiates sound because the hull vibrates and you might like to hear the sound and learn something about the submarine. On the other hand, you might be sending out sound beams and using them to look for submarines.

Zierler:

Allan, did you ever work in an official advisory capacity for the government on your work on nuclear detection?

Pierce:

I believe the answer is no. This goes back a long ways, maybe 50 years. I was typically a government contractor over most of my career. However, I was, for a while, maybe 20 years ago, an advisor to the Nuclear Regulatory Commission. This was when I was with Boston University. The NRC had a division which I believe was called the Nuclear Reactor Safeguards Department. The amount of power a given reactor was allowed to produce was regulated, and the NRC allowed the reactor operator to request the amount of power to be upgraded. This upgrade conceivably could lead to accidental incidents involving the release of radiative energy to the environment. Such accidents could be caused by structural failure caused by vibrations caused by fluid flow past structural components. I believe they had had one such near-failure incident previously. Every time a reactor operator requested the upgrade permission, there were a lot of studies and tests. Outside people were brought in as advisors to assess whether such would be safe. I was the person concerned with vibrations of the internal components of a reactor. My memory is a little dim, but I believe I was sworn to secrecy on the proceedings of the hearings.

Zierler:

What kinds of sonic booms have you studied?

Pierce:

Mostly, I have studied these generically. The sort of question I addressed was what happens to a sonic boom as it propagates through the atmosphere. I would say that the sonic booms which the public are interested in are mostly those associated with aircraft. But any high amplitude sound propagating long distances through the atmosphere produces a sonic boom. One problem with sonic booms, insofar as the public is concerned, is that they make big bangs. It has been a long-standing task for NASA to design low boom airplanes. Many years ago, in the 1960’s, Boeing and Douglas were trying to get our government to allow the manufacture of a supersonic transport. At that time, I thought they were going to, but the main complaint was that supersonic transports, if they actually made them, would make too much noise. This would be especially bothersome if they flew across the continental United States. And so, Congress put the squelch to the supersonic transport. But the British and the French, they made one, and they flew them across the Atlantic. But they didn't do this for too long a time, as the economics wasn’t quite right.

Zierler:

What has been some of your work on noise pollution?

Pierce:

Noise pollution? There are lots of things that make noise, and I have found it interesting to ask just how they make noise. If you don’t like the noise they make, you say it is polluting. And so, a lot of people do research to make a device a little quieter. One thing I worked on in this respect when I was at Georgia Tech were textile looms. Textile mills are incredibly noisy and they damage the worker’s hearing. When I was at Georgia Tech, I and a student, Glen Johnson, did a study of textile looms. These machines have things at the two ends which look like hockey sticks (pucks). These play something like ping pong with a little piece of wood (the shuttle) that carries thread back and forth across the loom, and when it hits the puck at the other end, it makes a big noise (a clack). And so you can learn how to make those sounds a little less irritating. We worked on that for a little while.

Zierler:

What are fluid-immersed shells?

Pierce:

Fluid-immersed shells?

Zierler:

Waves. The waves on fluid-immersed shells. I know you've done research in that area.

Pierce:

Fluid-immersed shells are hollow metallic structures buried in water. They could be cylindrical in shape or spherical in shape or any shape. A practical example is a submarine. The submarine is hollow, so that makes it a shell. But one of the things that we think about, in regard to submarines, is that when sound strikes the surface, it creates echoes that come back. If you're looking for a submarine, and it you think it's just a shell, you may be thinking too simply. There are other structures inside the hull that vibrate and which make it perhaps sound louder. Sound when it impinges on the surface creates waves that propagate around the shell and which radiates rays of sound back into the water.

Zierler:

Allan, a different question. To what extent have you needed to learn about the biology of the ear? In other words, the way that we take in sound?

Pierce:

I know something about this topic, but not much. I guess it would be nice to learn more about it and maybe I will do this someday if I can hold out much longer. I do worry considerably about what goes on inside the ear and the brain. Many of my friends have dabbled in this topic, including the late Sir James Lighthill. But you might be also interested in knowing that I have worked on bioacoustics and the sounds of insects. One of my colleagues, Derke Hughes, who actually worked for a Navy lab, and who made the news lately, studies cicadas. Cicadas are bugs, and they're sneaky little things. They only come out from the ground about once every 11 years, and when they do come out, they make a hell of a lot of noise. And so, my friend, Derke Hughes, who works at the Navy lab in Rhode Island, he got me involved and so we tried to quantity and understand the magnitude of the sound created by the cicadas. His idea as to the motivation for the cicada sound is that it's a mating call. A male cicada makes a lot of noise, attracts the female. Maybe the other way around. But this is what cicadas do. And it makes a hell of a racket when they're around.

Zierler:

Allan, tell me about your work as editor-in-chief of the Acoustical Society. How did that come about and what were some of your chief responsibilities in that role?

Pierce:

The Journal of the Acoustical Society of America goes back to 1929. It's old. And there were about five guys before me who had the jo. The Editor-in-Chief is the one guy who is responsible for making sure that papers are looked at and looked at properly, and that rational decisions are made. Th EIC decides whether papers should be published or not. I have dealt with publishing journals off and on back to 1973, and I was first an Associate Editor of JASA. Some years later, starting with 1993, I was co-Editor-in-Chief, with Ding Lee, of the Journal of Computational Acoustics.

One of my heroes, and this goes back a while, was a guy named R. Bruce Lindsay. He was a professor at Brown. And he had the JASA job for 28 years, starting with 1954. I always admired him and thought I might one day be like him. Lindsay died in office at at the age of 85, and another guy (Dan Martin) was in between. Martin lasted for about 14 years, and then he died too, and then I took over from him in 1999. The ASA advertised and I competed with several other guys, and I ended up with the job. I lasted 15 years and then resigned and was succeeded by my friend Jim Lynch. One of my chief tasks as EIC was the recruitment of Associate Editors. My predecessor believed that you needed very few AE’s, maybe only one for each major area. Some handled as many as 100 a year. I felt that each should handle of the order of 20 or les, and that we should substantially increase the number of AE’s and narrow down the scope of the areas they handled. In selecting who to ask, I asked for suggestions broadly and looked at the lists of papers published by the candidates in individual fields. I also looked at the papers that they had written, as I believed that quality of writing was extremely important. I also wanted editors who were broadly familiar with the literature and with the people working in the field. One of the most important tasks of an associate editor is picking reviewers, and you need to know who to ask and just how you assess the judgement of the reviewers.

Zierler:

What did you learn more broadly about the field of acoustics, given this central role in the field?

Pierce:

Who's the central role?

Zierler:

Yours. As editor-in-chief, you were uniquely positioned to really see the field from a focal point.

Pierce:

Well, I certainly tried to understand what everybody was doing. But acoustics is a very big and tough subject. And I was personally more engaged in what you would call the physics of sound, but there are also other people worried about the psychology of sound, and there are other people that worry about speech. How our speech is produced, how different languages are affected by speech. It's very complicated. It is also important that you know what has been done in the past. The Acoustical Society tries to encompass a lot of different branches of science. And I can understand some of it, perhaps most of it, but all-in-all, the work submitted to the Journal includes a lot of complicated stuff.

Zierler:

Allan, when did you first meet Bill Carey and realize that you would have such a substantial collaboration with him?

Pierce:

He came up to me at an Acoustical Society meeting sometime in the early 90’s and introduced himself to me. Actually, that happened to me a lot. Carey was a very outspoken guy. He was one of the leading researchers on ocean acoustics, ad had held positions at various Navy labs and at MIT. He was at the stage of his life where he was about ready to retire from the Navy civil service. One of my then present faculty members, Ronald Roy (now a department chair at Oxford), recommended Carey very highly. (We had built up a rather impressive group at BU during the early 90’s.) Carey liked to talk to people and he found we had similar research attitudes, so we talked a lot. Carey, after he came to BU, got one of the big prizes from the Acoustical Society called the Pioneers of Underwater Acoustics medal.

I didn't bother Carey too much the first few years in terms of research collaboration. But he did like to talk with me and with almost everybody about almost everything. He had a way of coming into my office and talking to me whenever he had the urge. Some of the times it was about the Middle East. And sometimes, it was about the Irish and about the Celts in general. He was a very outspoken guy. And he would sometimes come into my office and pose a question about some science problem he wanted to work on. At the time I wasn’t too immersed in specific research problems, because I was doing the journal, and that took a lot of time. At one time, Carey was very involved with mud. It may sound like a dirty subject to you, but it turns out a lot of the bottom of the ocean is mud. And there wasn't any decent theory of marine sediment mud. I came up with an intriguing theory having to do with electrostatic forces between clay particles, and Carey liked the theory and he got me to continue working on that. And so, we have a theory of how sound propagates through mud, and we involved Bill Siegmann and his students at RPI in this.

Zierler:

Allan, tell me about your decision to return to Boston after Penn State.

Pierce:

I had been at Penn State for five years and enjoyed it quite a bit. The students were excellent and I enjoyed the courses I was teaching. I also enjoyed interacting with my colleagues there, especially Gary Koopman and Vic Sparrow. However, my wife is an alumnus of Boston University and a native of Boston. She likes Boston. We lived very many places over the years, but she loves Boston. And more than Boston itself, she loves Cape Cod. So, I did have an extremely prestigious job at Penn State. One day, however, there was an ad in one of the professional magazines (maybe Physics Today) advertising a department head job at Boston University.

And I told my wife that they were advertising such a job. She's a BU alumnus. She got her bachelor’s degree at BU a long time ago. And she said, "You should apply for it." I applied for it. I wasn't particularly enthusiastic about the job after the interview. But I was nearing retirement age, and I thought maybe it was an ok way to end my career. My wife really was enthusiastic that we come back to Boston. So, I took the job.

Zierler:

The initial job was as department chair? You came in with those administrative responsibilities built in.

Pierce:

Yes

Zierler:

What was some of the work that you had to do as department chair?

Pierce:

Well, you had to assign classes. You had to make recommendations on whether people should get tenure. And you had to chime in on how much they should be given a raise. I tried to be very even handed. Anyway. most people there were fairly happy. Perhaps the most important thing I did was to initiate the hiring of new faculty members. The department had been shorthanded over the years and I wanted to build up a department with first class researchers. Many of the people I hired won prestigious prizes for their research. These included Ron Roy, Paul Barbone, Willian Carey, Robin Cleveland, and Leopold Felsen. There was also Michael Howe, who was hired just before I came. A common comment was “people are starting to sit up and take notice.”

Zierler:

Allan, what year did you retire?

Pierce:

Well, I think it was 2012. I had to stop being Department Chair when I took on the Editor-in-Chief job in 1999. I did have some substantial research grants for the next few years but was winding down for the final years. There was no way I could be Editor-in-Chief and Department Chair at the same time. I would have preferred starting the EIC job some years later, but such jobs come along whenever they do.

Zierler:

And did you have ideas to create businesses at that point? Or that idea came later on?

Pierce:

No, I still was working as the editor-in-chief. That was close to a full-time job. But after a while, I got tired of the editor-in-chief job and I still had a little of potential research output left in me, so I asked BU to allow me to work on a research grant which I brought in myself. I had a deal that I could work for BU after retirement part time on sponsored research. But I did this only for three additional years. The grant was a three-year grant and I worked out of my house (60 miles away). The grant lasted only from 2014 to 2017. The grant ran out and I came to the conclusion that I could run my research effort better than BU, and at much lower cost to the Navy. So, the next time that I asked for a grant, that was in 2018, I sent a proposal directly to the office of Naval Research. And as I said, I charged them only 10% overhead. Which is rock bottom. And then the Navy was quite happy.

And so afterwards the Navy also suggested to other people that they come and work with me. So I had about four guys then (myself, Bill Siegmann, Subramaniam Rajan, and Elisabeth Brown) working part time, but they were all working out of other places. All but one of these grants have now run to their conclusion, and I have decided that I am now too old to ask for any more. A colleague, David Brown, at the University of Massachusetts Dartmouth had told me that I had been flunking retirement.

Zierler:

Allan, in retirement you remained active with the article writing. I'm particularly interested in your work on Maxwell's equations and thinking about the special theory of relativity.

Pierce:

I had always had the feeling that much of physics ties together. I felt that Newton’s laws were really fundamental, not associated just with mechanics. I've always been curious about Maxwell's equations. I didn’t think Maxwell’s equations were really empirical equations, but I also don’t think you can actually derive Maxwell's equations from scratch. However, if you start with two ideas: one is that nothing goes faster than the speed of light (which is true) and you add another idea and stick to Newton’s laws, you are going to get Maxwell’s equations. The second idea is that the equations have to be covariant, the same in any Cartesian coordinate system moving at constant speed relative to the first coordinate system. You follow all the rules. You don’t start out with Maxwell's equations, but you end up with them. It turns out you have to have a coupling between charged particles and the coupling is in the form of fields. Whatever the fields are, they are going to obey Maxwell's equations. There's no choice. Maxwell's equations are derived from the idea of fields. So, I did that. Maybe I shouldn't have done it, because I was stepping out of my primary realm of activity. And this wasn’t really acoustics.

Zierler:

Allan, you've received so many awards in recognition for all of your contributions to the field. Is there any one that stands out that's most personally meaningful for you?

Pierce:

Every award tends to honor its donor and I am grateful for each one I received. I don’t think it is fair to the donors to try to rank them. Also, the previous winners add luster to each award. There is the Silver Medal in Physical Acoustics (ASA), the ASA Gold Medal, the Rossing Prize in Acoustics Education, the ASA Distinguished Service Award, the Per Bruel Gold Medal in Noise Control and Acoustics, the Gold Medal of the Acoustical Society of India, and various other awards. One that meant a lot to me at the time was an award I got as an undergraduate. The Chemical Rubber Company gave a copy of its Handbook of Chemistry and Physics to me for being the freshman physics student with the highest grades.

Zierler:

Alan, now that we've worked right up to the present, for the last part of our talk, I'd like to ask a few broadly-retrospective questions about your career, and then we'll end looking to the future. So first, I wonder if you could reflect on the value of your early interests in quantum mechanics, and what that has done to inform your research generally in acoustics.

Pierce:

Well, I think about it a lot. I probably think about quantum mechanics in a very simple-minded way. I think about what it means. And I think it's something to keep thinking about. I don't know if I've figured it out yet.

Zierler:

Given how early and important your article, “Extension of the method of normal modes to sound propagation in an almost-stratified medium” What has needed to be updated since you wrote that, and what has stood the test of time?

Pierce:

I guess it has stood the test of time. It is my most-cited paper. It was written back in1965, when I was at Avco. The idea came about basically when I was working at the RAND corporation, and it is basically an adaptation of a theory on which I based my doctoral thesis. That theory is a quantum mechanical theory and goes back to a couple guys: Max Born and J. Robert Oppenheimer. Their theory, called the Born-Oppenheimer approximation is a big deal in the quantum mechanics of molecules, at least it seems so to me. My thesis advisor, Laszlo Tisza, at MIT got me onto this. (He had an idea about superconductivity that unfortunately didn’t work out.)

The basic idea of the Born-Oppenheimer approximation is that a molecule is governed by a partial differential equation with many degrees of freedom and these are coupled, so that you can think of some coordinates as moving rapidly and some moving slowly. Those moving rapidly correspond to the electrons and those moving rapidly correspond to the nuclei. The main reason all this comes about is because the electrons weigh a lot less than do the nuclei. The electrons whirl about and find an energy eigenstate that has an eigenvalue. This eigenvalue depends on the instantaneous positions of the nuclei positions in a static manner. The electron motion adjusts adiabatically to the nuclei positions. The nuclei sense this energy state as a potential field and this field governs their vibrations. The carry-over to waves in “almost-stratified media” is that the vertical coordinate corresponds to the electron coordinates and the horizontal coordinates correspond to the nuclear coordinates. The horizontal coordinates satisfy partial differential equations with horizontal wavenumbers as parameters. These are eigenvalues that come from solutions for the vertical wave numbers. The correspondence is subtle but rather striking once you see it. One thing that it predicts is a phenomenon called horizontal refraction, The sound in a waveguide propagates along guided modes, but these, insofar as horizontal motion is concerned, propagate along horizontal rays, and these rays bend horizontally. The basis idea caught on well with workers in atmospheric acoustics and ocean acoustics.

Zierler:

Allan, you're known to always have a historical perspective and appreciation for the field of acoustics.

Pierce:

Yes.

Zierler:

Why is that so important for you?

Pierce:

I don't know. But we are all sort of set up by events that happened in the past. You really want to know how ideas came about and how they tie in. A guy I sort of admire a lot is Lord Rayleigh. His real name was John William Strutt. I have read his books and many of his papers and thought about all of them. I have also read his biography, written by his son. When I received the Rossing prize, I had to give a talk, so I chose to talk about the education of Lord Rayleigh. I am fascinated about the history of science, and recently published an article about the early history of vibrations in the Journal of Theoretical and Computational Acoustics. I wrote a lot about Galileo who did research on sliding bodies and who came up with a theory about pendulum oscillations. Much of acoustics started with Galileo, but you can’t say that too smugly. There is also Huygens, Newton, the Bernoulli’s, Euler, Lagrange, and lots of other clever guys.

Zierler:

Allan, I wonder if you've ever reflected on how your educational interests have really influenced the growth of acoustics generally in the United States?

Pierce:

I doubt my interests have influenced the growth of acoustics too much. Perhaps they have affected the way people tackle problems. Perhaps they have affected what problems people choose to tackle. I do argue a lot with people, but I don't believe I convince people I argue with much. But it is a lot of fun.

Zierler:

In what ways do you see younger scholars in the field taking on new areas of research, and in what ways are they continuing even the things that you were working on 50 or 60 years ago?

Pierce:

We live in modern times where you've got to make a living. I think often of Lord Rayleigh, who didn't have to work for a living. I was constrained somewhat because I had to work for a living. And so younger scholars probably get a job where they get paid. I think most of them enjoy what they did or do, but I don't think they have a great choice at what they do. An important thing is the attitude they have when they start a new problem. I am not sure that today’s younger scholars have a proper attitude when they start a new problem.

Zierler:

Given your long tenure and association with the ASA, in what ways has it changed over the years and in what ways has it remained true to its original founding? At least as far as you saw it?

Pierce:

I do feel that the level of mathematics in papers presented at meetings or submitted to the Journal has decreased quite a bit. There's not as much theory, of mathematical theory, in the subject as before. I play a game ever so often. I still get the hard copy of the journal, and of course I've gotten it since 1961. And it's very heavy. And I sometimes comb through the journal, trying to see if I can find an equation. Sometimes you have to look a long time before you see an equation. Then there is the question of what is the biggest: the number of authors or the number of equations. I suspect most of the authors do not have anything near the education I had when I was beginning my career. Much of what passes for research is simply numerical experimentation, without much in the way of theoretical guidance. There doesn’t seem to be much thought in the papers that are presented or submitted.

Zierler:

Allan, in what ways have the advances in computers, computational power, been relevant for your research over the course of your career?

Pierce:

They have been relevant of course. It is now possible to do simulation studies of many things that would earlier would have been very time consuming. Computer studies seem to me often to have been somewhat of a big distraction. Numerical studies are important, of course, but I get the impression that there is not all that much deep thought. There is an old rule I remember from a book on using computers in science. “Think first, code later.” This has been a problem for the past 50 years, but it seems to have gotten worse.

Zierler:

Allan, for my last question looking to the future, what remains interesting to you and what are you most curious about following as acoustics continues to develop?

Pierce:

Well, I'm interested in almost everything, but I would like to know how to tie ideas together. There's always something to be interested in. One thing I am currently interested in is the statistical aspects of acoustics. Some problems do not have clear-cut answers and we need to put probabilities on the possible answers.

Zierler:

Well, Allan, I want to thank you so much for spending this time with me. I'm so glad that we connected and that we were able to do this. So, thank you so much.

Pierce:

Okay.