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Oral History Transcript — Dr. Manfred Schroeder

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Interview with Dr. Manfred Schroeder
By Gerhard M. Sessler
At Waikiki Honolulu, Hawaii
November 30, 2006

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Manfred Schroeder; November 30, 2006

ABSTRACT: Family and educational background, University of Gottingen (1947-1954), attending a lecture by Werner Heisenberg; reasons for his career in physics; details about his Master's and PhD theses and work at Bell Labs; research at Bell Labs (1954-1969), working with Winston Kock, Ralph Miller, work environment; professor at the University of Gottingen (1969-1991); information about his publications, his wife and children, and his hobbies — computer graphics and bicycling.

Transcript

Sessler:

From the Darmstadt University of Technology. I’ll be interviewing Manfred Schroeder. Today is November 30, 2006. We are here at the Sheraton Waikiki in Honolulu, Hawaii. The site of the Fourth Joint Meeting of the Acoustical Society of America and the Acoustical Society of Japan. The meeting is presently going on. Just yesterday we had a special session in honor of Manfred Schroeder. Let me, before we get into the interview, say a few words about Manfred. Manfred studied physics at the University of Göttingen from 1947 to 1954. He joined Bell Labs in 1954 and became department head there of Acoustics Research in 1958. In 1963 he was my director of Acoustic Speech and Mechanics Research. In 1969 he returned to the University of Gottingen as a professor. He became an emeritus in 1994, I think.

Schroeder:

In 1991 I became an emeritus.

Sessler:

In 1991. Yes. Manfred received many honors and distinctions. Let me just mention a few of these. He was awarded the Gold Medal of the Acoustical Society of America and the citation reads something like this. “For theoretical and practical contributions to human communication through innovative application of mathematics speed, hearing and concert hall acoustics.” He also received the Gold Medal of the Audio Engineering Society. He received the Rayleigh Medal of the British Institute of Physics, which is their highest award; the Helmholtz Medal of the German Acoustical Society, the DEGA, which is also the highest award of this society. Then he received the Rhein Prize, which is the highest award in Germany in communications engineering. He received the State Prize of the State of Lower Saxony. Manfred is a member of the National Academy of Engineering, a member of the American Academy of Arts and Sciences, a member of the Göttingen Academy of Sciences. He is a Fellow of the New York Academy of Sciences. He’s a foreign scientific member of the Max Planck Society, a Fellow of the Acoustical Society of America, the IEEE, and the Audio Engineering Society, and he’s also founding member of IRCAM, the Institute, de Recherche Acoustique Musique in Paris. Manfred authored many publications and several books. For instance, a book on number theory and fractals and chaos, and then there’s another book on computer speech.

Schroeder:

Yeah, and then I edited a book on speech and speaker recognition.

Sessler:

Yes. Well, this concludes the introductory remarks. Let’s now start with the interview, and I will first speak a little bit about Manfred’s youth. Manfred, I know you were born in Ahlen, Germany in 1926, but I don’t know very much about your family. Could you tell us a little bit about this?

Schroeder:

Yes. My father was an engineer. He worked in a mine in the Rohr District. And, in World War I he was a combat pilot and he always liked flying. So even after the war he founded a private flying club in Germany and flew small planes. And then when the German Air Force was reconstituted in 1935, since his heart was always in the air, so to speak, he became an Air Force officer. But, to his great regret he was now too old. He never flew a plane again. He was just a pencil pusher [Laugh] in the German Air Force, and, until he was dismissed in 1944 because of his attitude toward the German policies in Russia. He was moved out of Russia, never promoted again after 1941, and then finally dismissed in 1944. And other than his small pension, as a result of his not being promoted, there were no further consequences for him.

Sessler:

What kind of education did your parents have?

Schroeder:

Well, both my parents went to German high school and got their abitur, their school-leaving diploma from a German high school, which is roughly equivalent to having done high school and two years of college in the United States, I believe.

Sessler:

Were there any secondary school teachers, or perhaps other people, who had a particularly strong influence on you in science or in other fields?

Schroeder:

Well many, if not all, of my mathematics teachers encouraged me in the direction of science, physics, and mathematics. I remember one mathematics teacher who leant me his telescope so I could look at the moon, and the stars, and then the next day report to the class what I had seen. And there are many other instances like this where I was sort of “promoted” by my science and math teachers. Once, I remember, the teacher was explaining the Doppler Effect: the frequency of the approching source goes up and then it goes down, but then when he wanted to apply the Doppler Effect for a source that was not directly headed for the listener but at some distance, he got stuck. [Laugh] And, he called on me and I explained it to the class. I mean, all you need is a little Pythagoras and a little differentiation until you get the right answer of the Doppler Effect if the source passes you by at some finite distance.

Sessler:

Yeah, I wonder what, of all these things, all these people, you think had the greatest influence on you while you were growing up?

Schroeder:

On what?

Sessler:

The greatest influence on your future career?

Schroeder:

Yeah. Well, as I said there were many teachers. I already mentioned two, and another one, for example, appointed me sort of his personal assistant for the physics lectures that involved demonstrations. And, one of the greatest influences was my grandmother, because since – I always wanted to become a mathematician. I was strong in mathematics, so to speak. But, my grandmother always said, “Der Manfred wird mal eine Physiker.” “Manfred will become a Physicists.” And, she was right. So, when it was time to sign up as a student I signed up as a student of physics at the University of Göttingen.

Sessler:

So, you expected from early age on to go to college? And, when you first went to college, what did you expect your education would lead to?

Schroeder:

Yeah. Yes. There was never any doubt that I would go to higher, to the university. And, even my father, I forgot to mention that, I said, he was an engineer, a mining engineer, and he had gone to technical college. And so, it was always clear that I would study. And then after World War II, when I was twenty, twenty-one, I opted for the University of Göttingen because Heisenberg was there, the famous physicist, and Von Laue was there, another famous Nobel Prize winning physicist. And of course, Göttingen still had a very high reputation. So, I applied at Göttingen and I was accepted there after some hurdles. Namely, I was asked by one of the examiners there what I had done during the war and I said, “I summed trigonometric senses.” And he said, “Well, how do you do this?” I said, “Well, using the addition theorems for sine and cosine functions.” And he said, “You never heard of the complex exponential? If you had done it with complex exponentials you would get a geometric series to compute the directivity patterns of your antenna arrays,” what I was interested in.

And, I knew this man was right and I was really too stupid for this university. And then luckily Becker, the main examiner came and the same question, “What did you do during the war?” And I stayed away from trigonometric senses and said, “Well, I worked with electronic circuits.” And Becker said, “Well, go right ahead.” And for about fifteen, twenty minutes I said everything I knew about oscillating circuits and electromagnetic radiation, and damping and all these things, and then Becker said, “Okay, that’s enough.” And I thought, I was so shy, I thought this is enough to be immediately dismissed. And so, since my whole career was in the balance I asked Becker, “Well, what are my chances to be accepted here at this university?” And Becker said something that I will never forget. He said, “If you’re not accepted nobody will be accepted.” [Laughter]

Sessler:

Very nice.

Schroeder:

Thank you Professor Becker.

Sessler:

Now, if you’ll talk about your undergraduate teachers up to the Vorduplom (B.S.). Were there any particularly strong impressions, you know, any people who stand out?

Schroeder:

Yeah. Well, I went to attend Heisenberg’s lectures on the shell model of the atomic nucleus, which had just been proposed by Maria Goeppert Mayer and two collaborators, and but I didn’t understand a word. Because, this Heisenberg lecture was aimed at higher semesters and I was only in my second or third semester. So, I later got to know Heisenberg personally, but as a teacher he dropped from my horizon at this point because it was simply above my head. The teacher that influenced me most was the Professor Becker, Theoretical Physics, that I already mentioned. Becker had the saying, “Don’t calculate. Think.” A little bit like Dick Hemming who said, “Don’t compute. Think.” (

Sessler:

Yeah.) He was a very influential teacher. And here is another incident that I might recall from a mathematician I met and which I and everybody else regarded very highly, Rellich. And when I started my PhD thesis I had a question about the distribution of eigenvalues for cavities, electromagnetic cavities with losses. But, Weyal had only proved the case of real eigenvalues corresponding to the case in physics of no losses and I wanted to know whether there was a theorem that explained the distribution of eigenvalues in the case of lossy cavities. And he spent about twenty minutes in the library and then turned back to me and said, “We are very sorry. There is no such theorem. You’re on your own.” And then he said a very interesting thing. This was in 1952. He said, “Do you know that you are the first physicist who comes and asks us mathematicians a question?” Because in the 1930s, before Hitler came to power, there was a very close collaboration between the mathematicians at Göttingen, Hilbert, Klein, you name them, and the physicists, Max Born, Werner Heisenberg, and so forth. And when the Nazis came in, this completely disappeared, this kind of collaboration, though Professor Rellich said, “You know, you are the first physicist to see us in twenty years with a question?” Okay, so obviously Rellich had a positive influence on me, and other teachers of course too.

Sessler:

So you, of course, had made up your mind that you wanted to establish a career in physics. Now, what attracted you? Was it the fact that you could do research there or did you want to be a teacher, or what?

Schroeder:

Well, first of all what attracted me to physics other than the prediction of my grandmother that I would become a physicist, was theories like Einstein’s, which we were able to understand, and theories, quantum mechanics by Heisenberg, which we didn’t understand. And, I wanted to understand this and I wanted to become a theoretical physicist to understand the underlying principles of physics, especially as I already said, quantum mechanics because we considered, general, or special relativity sort of duck soup by comparison with quantum mechanics. I mean, relativity tells you that, general relativity, that curve is spaced. I mean, space is curved. (

Sessler:

Space is curved? Yeah.) [Laugh] Sorry. And that simultaneity and ether are fictions of the imagination. Okay, that’s all relatively simple, no puns intended, relatively simple to understand about relativity theory. But, quantum mechanics is a completely different thing. As Richard Feynman once said, “I think it is safe to say that nobody understands quantum mechanics,” Richard Feynman. Or, Niels Bohr said, “If you don’t get dizzy from studying quantum mechanics you haven’t understood it.” End of quote by Niels Bohr.

Sessler:

Yes. So, what sort of life did you expect to lead as a scientist when you chose this career? What sort of a job prospect (

Schroeder:

Yeah.) did you see?

Schroeder:

Well, I thought I would become a theoretical physicist, but honestly I must say I discovered pretty soon that there are some people about my age, in theoretical physics, who were better than I if not much better than I, and that well I would become a good theoretical physicist but maybe not another Einstein, or a Feynman, or, and so forth. And then sort of fate intervened. I attended a laboratory, advanced laboratory course in experimental physics, which was a requirement for a physics student, even a prospective theorist. I never liked laboratory courses. After all, I was a future theoretical physicist, but you had to do it. And, I became only interested in the experiments that I could sort of, the German word is únfúnktoureve where I could change the direction of the experiment. Example, one experiment was to measure the velocity of light on a cable rolled up in the basement of the physics building by measuring the delay, so and so many microseconds and then divide, this into the length of the cable and you would get the speed of light. And I thought it’s much easier, I take the end of the cable and connect it to the input of the cable through an amplifier, crank up the gain until howling starts, and then I measure this frequency at which the cable howls, and take a slide rule and it’s reciprocal and so forth and I get the delay and I get the speed of light on the cable. For me this was almost self-understood to do it that way. But it attracted the attention of the director of applied physics institute in Göttingen, Erwin Meyer, and he invited me to join experimental physics, applied physics. So, at this point I left theoretical physics, you might say, from theory into experimental physics and I’ve been very happy in applied physics ever since.

Sessler:

What was your family’s attitude to your choice of this career?

Schroeder:

Well, my family, of course, was very happy. Not only my grandmother, but my father, as I’ve already said was an engineer, mathematically very gifted. Even my mother was mathematically gifted. So, they were very happy to see their only son go into science, specifically physics.

Sessler:

Of course, you chose to go to Gottingen University, you already mentioned this, because there were many famous people there. And, when you started your studies how were you supported, then later on also as a graduate student?

Schroeder:

Yeah. That’s a good question. In 1948, one year after I had begun to study, there was this currency reform in Germany and the little money that the family had, of course, disappeared overnight, and the new money, the Deutschmark was issued, and my parents had very little, and they supported me to the tune of sixty marks a month. That would be $15 or so. In other words, even in marks it wasn’t very much money. And, I couldn’t pay the tuition so I did a special examination to get excused from paying the tuition, and I took such an examination with Professor Kopfermann, a real gentleman I might add, and he asked me all kinds of questions and I answered them, and then he came to a question I didn’t know what he was talking about. And, he said, “Well, this was part of the course that accompanied the laboratory course.” I said, “I went to the accompanying course only once because it was so bad,” It was given by Professor Paúl, who later won the Nobel Prize in physics, “And so, I never went again.” Then Kopfermann said, “But wait a minute, Professor Paúl, is only a phonograph record. The lecture is by me.” I said, “Well then, he’s a very bad phonograph disc.” And then Kopfermann rose. End of interview. I rose too. “Well, I will never get a tuition reduction. Then about a week later I get a phone call from the Academic Assistance Council: Professor Kopfermann had approved my tuition-free request and had also asked whether I didn’t need some extra cash. And I said, “Well, come to think of it, yes, I do need extra cash.” So, thanks to – you know, this shows what kind of a gentleman Kopfermann was. In other words he rewarded not only that I knew my stuff but he rewarded the fact that I didn’t hesitate to tell him that his assistant was a very uninteresting phonograph disk.

Sessler:

Now, Professor Kopfermann was the director of the First Physics . . .

Schroeder:

Professor Kopfermann was director of the Second Physics Institute called Atomic and Nuclear Physics.

Sessler:

I see. Yes.

Schroeder:

And . . .

Sessler:

What was your first real research project? Was it your thesis?

Schroeder:

Well, yes. Even before joining applied physics while I was still working in theory. I had my first scientific publication in specific heat of certain metals, and the paper, my very first paper in 1952 I believe, was on the representation of the specific heat by Einstein and Debey terms. I don’t want to go into detail but it as a very nice paper and the original idea, of course, didn’t come from me. But, Brenig and I elaborated this idea and it made a very nice paper and this became my first publication, as I said, in theoretical physics. All my later papers were then in applied or experimental physics.

Sessler:

Yes. You got, of course, your training at Göttingen University, but I think you spent also some time elsewhere? Could you comment on this a little bit?

Schroeder:

Well, once I had my diploma, my Masters degree in physics, I had enough of the university and I wanted to get my hands dirty, so to speak, and work in industry. So, I went to Nuremberg and joined the Grundig Radiowerke. And they were just beginning to manufacture TV sets, this is 1952, and they needed test equipment to test their TVs as they were being produced. And, I was very successful with some impulse generators to test the video part of the TV. And, they were so impressed that they wanted me to stay. And, I might have stayed because, as I said, I liked the applied work. I liked to get my hands dirty. But then I had promised my professor in Göttingen, Erwin Meyer, whom I have already mentioned, that I would return for doing a thesis and PhD, because Meyer felt that one should have a PhD to get ahead in life, and I think he was right. I would have never landed at Bell Labs, for example, without a PhD.

Sessler:

Yes. You have not told us anything about your PhD thesis yet. Perhaps you can comment a little bit on this and your work in Erwin Meyer’s Institute?

Schroeder:

Yeah. Okay. What you first had to do before being fully accepted in the institute was to build up an experiment for the laboratory course with new experiments which came out of technology that had been developed by Germany and even more so by the allies during the war. So, Meyer asked me to set up an experiment with round waveguides to measure the wavelengths of the different modes H10 we called them then. Now it would be TEM11, or whatever. And, I told Meyer, “Look, round waveguides mean Bessel Functions and I don’t like Bessel Functions.” And Meyer said, “The only things you have to know about Bessel Functions is 1.84 and 2.40, and so forth, related to the zeros of the first Bessel Functions and their derivatives.” And Meyer was essentially, right. You could work with round waveguides without knowing much about Bessel Functions. But, one thing I discovered that the resonance of the fundamental mode, as I said, what we called the H10 mode, always showed two resonances right next to each other and nobody at the university could explain to me what was going on. Even some very good theorists. And I finally came up, had to come up with the answer myself. And I said to myself, “Look, the fundamental mode in a round waveguide, that’s like vibrations in a kettle drum, the diaphragm of a kettle drum. In the kettle drum that mode corresponds to H10 mode in waveguides, there are really two polarizations.” In other words, there are always two resonances at exactly the same frequency if the waveguide was exactly round, but of course no piece of hardware is exactly round, or whatever.

So, the two frequencies, at roughly 10GHz, are slightly split apart. And that’s what I was observing. But it took me a long time because I had a little detector that was polarization sensitive. And, when I turned it by ninety degrees I didn’t go from one mode to the other, but some complicated thing. And then I figured, “Well, my little magnetic loop that measured the polarization was part of the perturbation.” And therefore, I kept the loop fixed and turned the whole transmitter, that I used in this experiment, and then it was clear it was exactly the two polarizations. This turned out to be a very nice laboratory experiment. And then, when it came to selecting a topic for my masters thesis I proposed it. I said to Meyer, “Look, this is actually a sensitive method. How about using it to, measure dielectric constants of Plexiglas and other substances, insulators, at 10GHz, three centimeter wavelengths?” And this, in fact, became my master’s thesis; The Measurement of Various Material Constants in Microwave Cavities by Degenerate Modes,” by the splitting up of degenerate modes. And this turned out to be a very successful enterprise with precision measurements of these material constants at very high frequencies.

Sessler:

And do you want to comment a little bit on your dissertation? We have not covered this yet.

Schroeder:

Yes. As I said, after the Master’s thesis I went to Grundig, but then I, as I promised Meyer, after six months I returned and started my dissertation. Meyer had money for a dissertation project from the Rome Air Force Research Command, or whatever it is called. Rome, not Italy, but Rome, New York. And, in acoustics, you know. And I told Meyer, “Look, I’m not interested in acoustics. I’m interested in microwaves. And right now I’m using my microwaves on old discarded American army biscuit tins. And when I shake all the crumbs out I get thousands of resonances at three centimeter wavelengths, and I’m interested in the statistics of this.” And, as I said, I abhorred acoustics. Ya. And so Meyer, the great diplomat, not just a good physicist, said, “Okay. You do your experiments on the statistics of resonances in microwave cavities, as you want to, and we will interpret the results in terms of the distribution of resonance in concert halls. So, my thesis, fourteen months later, appeared under the title, Resonances in Large Rooms and Concert Halls, subtitled Experiments by Microwaves.

Sessler:

Yes, this of course was, the results were of very much interest in acoustics (

Schroeder:

Yes.) and would you like to comment on this?

Schroeder:

Ya. Well, people always thought various things related to the transmission curve as a function of frequency from one point to another in a room were very important and I was able to show, in subsequent work, that these transmission curves in rooms above a certain frequency, that is now called the Schroeder Frequency, are completely random. They are, technically speaking, essentially a complex Gaussian process in the frequency domain. So, I could use the results of S.O. Rice, a mathematician from Bell Labs, and my theory proved to predict everything you wanted to know about such responses in concert halls. And this came as a big, big surprise in room acoustics. Dick Bolt, for example, of BBN and MIT, and others, had banked on these responses as explaining differences in quality of the different concert halls, and I showed these are just random functions. [Laugh] And so, then I very much impressed Meyer, of course, and others too, and Meyer said I should go to America, and then I wanted to go to Bell Labs because I had heard about Claude Shannon, and so forth. But Meyer said, “They don’t take any foreigners.” I had a student in 1938 who was rejected by Bell. But then, in 1954 Shockley came to Gottingen and he’s looking for physicists. And so, I went back to Meyer and I said, “Look. Bell Labs is even looking for foreign physicists,” and Meyer wrote a letter the next day to the director of Acoustics Research at Bell Labs, Winston Kock and within two weeks I had an answer to meet Koch for an interview in the lobby of the Dorchester Hotel in London. The interview apparently went very well and Kock told me, “But, it will take about six weeks,” because I was not an American citizen, I was a foreigner, and the president of the company had to approve this, and that would take about six weeks. And almost to the day six weeks later I got this very nice offer of permanent employment in the Research Department of Bell Labs.

Sessler:

So, you were offered a job at Bell Labs and you decided to go to the labs, accept the offer?

Schroeder:

That’s right. I had to finish some work for Rome Air Force, New York, at Gottingen, and then in September completed all my obligations in Germany. And, I always liked Italy very much. I had studied Italian in Pisa. So, instead of catching a boat from a German port I went to Italy to Genoa and caught the Andrea Doria there and sailed for New York and arrived on September, 30, 1954, to report to Bell Labs. And, at the pier waiting for the immigrant Manfred Schroeder was a long black limousine, chauffer-driven, with my future director Win Kock and my supervisor Ralph Miller. I think few immigrants were received in such style. And instead of going to Bell Labs right away we went to one of the fanciest restaurants in the area for lunch, namely the restaurant Newarker, at Newark Airport. It doesn’t exist anymore. But, that was one of the best restaurants in the Northern New Jersey. And so the menu, of course, was in French. I couldn’t read any French menus, although I’d studied in Paris, but menus were beyond me. And, I recognized only one word there on the menu, the German word “bratwurst’. So, I ordered bratwurst, and Kock and Miller were so polite. Everybody ordered bratwurst, and then I spotted Lowenbrau beer, and everybody had a Lowenbrau beer, and that shows how polite they are. At the same time, at neighboring tables, flaming desserts were going off, but we had the bratwurst and Lowenbrau beer in this fancy restaurant.

Sessler:

And such mistakes didn’t happen to you, later on —

Schroeder:

Right.

Sessler:

— such mistakes didn’t happen later on in your career to you? [Laugh] Ordering the least expensive —

Schroeder:

Yeah. Yeah.

Sessler:

— beer!

Schroeder:

The chauffeur was waiting for us and we took off for Murray Hill. The first point of contact, of course, was the medical department to see that I was in good health. And then I was put on the payroll. And, yeah, this was Thursday, September 30, 1954, one of my most memorable days, both that day and the next few days. The next day, Friday, was my first full working day at Bell Labs. I was shown the ropes by Floyd Harvey. And either Kock or Harvey apologized to me for the low salary, and but they said, “We have a self-service stock room to supplement your income.” [Laughter] And, then on Saturday I had a day off. And, with the housing consultant of Bell Labs we found a room for me in Summit, New Jersey for $15 a week, a nice room. Then I walked into a used car lot there and they, when they heard my English they immediately switched to German, and they had just the right car for me. “How much money did I have on me?” Well, I said, “A hundred dollars.” They said, “You leave $50 here and the car over there is yours.” And, I left them $50, and of course everybody assumed, when I told the story, that I was gypped, but in fact the car that they sold to me, as they had pointed out, was in very, very good condition, driven by an old lady who had it always serviced and so forth. So, it served me for another ten years, and at a reasonable price. And then the next day, Sunday, I didn’t have a license yet and I took the Lackawanna train to Hoboken, and then the Ferry to Christopher Street. I must admit I’d never been in a taxi before. There was only one taxi there and two people were already sitting in it. I hopped in with them and nobody said anything. I think the driver immediately knew what was going on, namely that he was capturing a complete greenhorn. Well, in any case, he drove the couple to the East Side and charged them what was on the meter. He kept the meter running and then drove me to the West Side to visit a young woman whose address I had. And, I paid again what was on the meter $18.30. I still remember. That’s more like paying $40 now, maybe, but it was certainly worth it, because the young lady I met on my third day in the United States, after this “expensive taxi trip” not much later became my wife and mother of our three children.

Sessler:

Now, what were the working conditions at Bell Labs in those days, your equipment, your colleagues, the freedom you know, in respect to your research topics, (

Schroeder:

Yeah.) your salary, and so on?

Schroeder:

Well, of course, the atmosphere was very friendly and open at Bell Labs because, as opposed to IBM, you didn’t get any money for patents. Nobody had any secrets. I learned a lot, a lot by osmosis at Bell Labs. I was a physicist, yes, and a kind of a mathematician but I didn’t know anything about electrical engineering and other things. I learned at Bell Labs. So, a very friendly and open atmosphere. Now, in terms of support – anything you wanted for equipment. You didn’t have to write any proposals, except so-called “plant money” which was limited. If you wanted to buy an expensive oscilloscope or have a new building erected that would be a little more difficult. But, other than that money was flowing freely. And one of the reasons was, of course, that Bell Labs was the research arm of AT&T the American Telephone & Telegraph Company, and they could, in the ‘50s, and ‘60s, and ‘70s, up to 1984, write off the expense at Bell Labs as a business expense. So, all the zillions on dimes that Americans put into the coin telephones and so forth, AT&T could apply to supporting research. As I said, it could be written off as a business expense. So, money was never any concern in those days, and we could really do – well, I wanted to say, “Do whatever we would like.” Yes, I did whatever I liked, but it better be related somehow, however vaguely, to telephone or human communication. And so, when I arrived on the scene in Bell Labs, Kock suggested, my director suggested that I continue working on the statistics of large spaces, cavities or concert halls. And I thought, typically naïve a twenty-eight-year-old that people had solved all the problems in room acoustics. In any case I wanted to work in a field more germane to Bell Labs and AT&T. And, I picked speech on my first or second day at Bell Labs. I picked speech as my research field. I didn’t know anything about speech and nobody cared, but as I said I picked up a lot by osmosis and and speech remained my major research topic to this very day, fifty-two years later. And I picked it because I felt, “Well, I should do something useful for this nice company.”

Sessler:

Was this one of the specialties that existed in your department, and what were the other specialties there?

Schroeder:

Yeah. This was called the Acoustics Research Department. Actually, now we call it Acoustics Research Center, which comprised four departments. One was called Acoustics Research, having to do with acousticalography (?), among other things, and loudspeakers, and microphones, and so forth. And one under Harold Barney, which was called Speech Research Department. And, I forget what the other two of the four departments were called, but one was called Speech Research, and I became associated with that work. Actually, my first department was in the Acoustics Research Department and so I was directly under Kock, even as a department head, and as a director. But, what I did, of course, was of my own choosing, namely speech research. So, there was a lot of interaction with the speech people there, like Hugh Dunn, and Harold Barney, and Homer Dudley, and all these “ancient” speech people.

Sessler:

Yeah. You mentioned Win Kock. What was his style as a leader?

Schroeder:

Well, Win Kock’s main forte was to enjoy life. For example, when he had to go to Europe, to Scotland, on some underwater sound work he never flew. He took the Independence or Constitution, a transatlantic liner, and not to Loch Ness or London but to Cannes in France, and spent a day on the beach in Cannes, and then spent a day or two in Paris, and then spent a day or two in London to interview Manfred Schroeder and other “important projects.” (

Sessler:

Uh huh.) And then eventually he ended up in Scotland doing his underwater sound work. In other words he had a knack for turning everything into his personal enjoyment. But, he was also a great inventor. He came from the Baldwin Piano Company originally, and also worked on microwave antennas during the war, very important work. And, he had many patents. I have to guess at the number but I think he had at least fifty patents, maybe more. And, some of these patents dated from his time at the Baldwin Piano Company, and which he had taken out as a private individual. So he, got the patent fees from those Baldwin Piano Company days. And so, as opposed to all the other research directors at Bell Labs, or most of them anyhow, he was “independently rich.” He had the biggest house in the area, and so forth, so that was my director Win Kock. And, as I said, when I arrived on the American shores he commandeered the biggest limousine to meet me. That was Win Kock.

Sessler:

Yes. Now, was there a good exchange of ideas within the department and within the center?

Schroeder:

Yes, there was of course. As I said, I didn’t know the first thing about speech and my first job was inverse filtering, and Ralph Miller was one of my major resources. Ralph Miller, my immediate supervisor, was in on the X Project during World War II, building the secret scrambling device for the telephoning between Churchill’s war room in London and Roosevelt’s offices in the White House. And so he had a long and important background in speech research, speech coding. Theirs was the first Vocoder which coded speech at 1,500 bits per second, and this was in 1942. It’s incredible they were doing this already in ‘42. But, they didn’t know they were doing it for Churchill and Roosevelt. This was secret. They just did it. And long after the war they learned [Laugh] who were their customers. Ralph Miller on a tourist visit to London after retirerment, discovers his equipment in Churchill’s war room in London. And then he finally knew for certain whom he had worked for during the war providing these secret speech links.

Sessler:

Of course you interacted with many people in the lab. There were many other people who you have mentioned before in other conversations, with whom you had an exchange of ideas, and whom you helped, and who helped you, in these projects?

Schroeder:

Yeah, there, as I said there was a constant exchange of ideas. Certainly the first few years I learned a lot more from others, about electrical engineering and so forth than they learned from me. On the other hand I must say that my background in mathematics and physics, albeit in different directions from speech came in very handy in my speech work and other work at Bell Labs. So my education in Gottingen in general physics and mathematics was by no means in vain, to put it mildly.

Sessler:

Well, let’s talk about some of the specific projects which you carried through while you were at Bell labs.

Schroeder:

Yeah.

Sessler:

Let’s perhaps first talk about speech and architectural acoustics.

Schroeder:

Yes. My first project, instigated by my supervisor, whom I already mentioned, Ralph Miller, was inverse filtering of speech. You spoke into a microphone and fiddled with some inverse filters long enough so that you would undo the vocal track resonances due to the pulses from your glottis, the puffs of air. And so, you could see on the scope, after you had done enough fiddling, the pulses of your vocal cords. This was one way electronically, so to speak, looking through your mouth beyond your teeth at what your glottis was doing. So, that was very interesting work and I learned a lot from that work. And then later I became, or even right away, I became interested in Vocoders the machines that had been used in this speech scrambling during the war. And, I was using it for bandwidth compression. In 1956 the first transatlantic telephone cable was inaugurated between the U.S. and Europe. Forty speech channels. And I worked then on Vocoders to turn those forty channels into 400 channels by a ten to one compression. To make a long story short, it was never used that way but the work I did and others at Bell Labs in speech eventually ended up in linear prediction and is now in every cell phone and every Internet acoustic signal. In other words, these things wouldn’t work without compression. Of course, we all know that pictures are compressed on the Internet but speech is also compressed, and it certainly is compressed for cell phones. You couldn’t have a zillion cell phone users if the speech transmitted through the air to the individual cell phones wasn’t highly compressed. And then in the cell phone the speech was reconstituted. A little bit like orange juice. You take the water out and ship just the frozen orange pulp, and then at the other end you reconstitute the orange juice. And then, I think this worked very well and I’m very happy with the work I did here.

Sessler:

What kind of compression ratios could be achieved?

Schroeder:

Yeah. Much of this work, especially on linear prediction, was with Bishnu Atal and I remember a code-excited linear prediction that we did around 1983, where for each sample of speech, speech was sampled 8,000 times a second, telephone speech, a bandwidth about 3.5 kHz, sampled at 8,000 samples per second according to Nyquist’s Sampling Theory, and then for each sample, believe it or not, we assigned a quarter bit. In other words, for four samples we assigned only one +/- 1 so to speak and we got perfect quality that you couldn’t tell from the original. Why? After 1976 we had the properties of the human ear in there – this was also with the help of Joe Hall—incorporated in our coders, and that led to this tremendous success. We achieved very high compression ratios at, at very high quality.

Sessler:

Yes. One of your hobbies, so to speak, was of course always architectural acoustics?

Schroeder:

Yes.

Sessler:

And, you did a lot of work in this field also. Would you like to say something about this?

Schroeder:

Well, after I joined Bell Labs, although Win Kock tried to encourage me to continue architectural acoustics and I sort of soft-peddled it, because I felt it wasn’t important for the telephone company, and I wanted to be a useful [Laugh] researcher on the staff. But then, in the sixties we were talking more and more about hands-free telephones, conference telephones where of course the room acoustics plays a role. So suddenly, my room acoustic knowledge came to the fore again. And then in 1963, when Philharmonic Hall, Lincoln Center, opened there was this acoustic, the acoustic problems and Lincoln Center asked AT&T for help, and AT&T asked Bell Laboratories, and Bell Laboratories then asked me. I was, at the time, director of Acoustics Research when this Philharmonic Hall acoustics problem landed in my lap. And a commission of four was formed under the leadership of Vern Knudsen, the former chancellor of UCLA. However, it was made clear to the committee of four that, yes, I could join them in this rescue effort for Philharmonic Hall in New York, but I couldn’t actually do any acoustic consulting. Because by the consent decree between the U.S. government and AT&T of 1956, AT&T was limited to the following fields: 1) Providing telecommunications, telephone; 2) Printing Yellow Pages, a hugely profitable business; 3) Provide an artificial larynx, transistorize artificial larynx at cost, that was $46 and was mentioned specifically; and one more thing, AT&T could do under this consent decree, namely do research for the government, the military mostly. And so certainly an AT&T person, Bell Labs person couldn’t do any acoustic consulting. So, this was understood that the only thing I could do to help the committee with was making measurements. So, Bishnu Atal and Gerhard Sessler, who is interviewing me now, and Jim West, and I developed new methods of digital analysis of concert halls, which was very successful, and we were able to point out the major deficiencies on an objective, measurable, reproducible basis. Carol McClellan Bird did the intricate computer programming.

Sessler:

Well, of course you, this was one very important contribution but there were many others in room acoustics, like measuring room reverberation times, and so on, you know.

Schroeder:

Yeah.

Sessler:

So, could you comment on some?

Schroeder:

Yeah. That’s a very good point. For example, I discovered in this process, the Philharmonic Hall Project, that established methods of measuring reverberation time had various deficiencies, and it occurred to me, by recording the impulse response and then inverting it in time or integrating it backward – this is now called Schroeder Integration – it gave you very good reverberation curves and very precise measurements, especially for halls that didn’t have an exponential decay of energy but where you had a multiple slope, two-slope decay. All these fine details of the reverberation process were brought out by this method which occurred to me around 1965. And another thing I invented later was, clear from our work at Philharmonic Hall and the work I later did at Gottingen that that there wasn’t enough lateral sound modern, many of these modern concern halls, so we needed more lateral diffusion, more laterally-traveling sound. And, I knew enough number theory to know that if we structured the surfaces, especially the ceiling of a concert hall, according to these number theoretic principles specifically, quachratic? residues, then we would get a much better acoustic quality. I didn’t earn a penny on these patents.

I did get one dollar, yes, on my first day at Bell Labs. But, Bell Labs actually never took out a patent on this but we published it and then it was in the public domain and various American and other European companies then produced these quachratic residue diffusers, called QRD diffusers, So that was another contribution: Sound diffusion in concert halls. In the meantime, in the ‘60s and ‘70s sound diffusion were also used in churches, in schools, even in private homes. I remember a reporter from Forbes magazine who went to a private home where a person had such a number theoretic diffuser and the reporter asked the owner, “What is that over there in the corner?” He said, “That’s a Schroeder box.” “What does a Schroeder box do?” “Well,” the person said, “I don’t know but it makes a wall disappear.” In other words, what these diffusers did they took away the harsh reflections from a wall, even in a living room, and laterally diffused them into a broad, soft pattern you might say. Incidentally I didn’t understand the title of this article in Forbes magazine about my own diffusers. The title was, Applied goes into Hm, what does “Applied goes into” mean? I didn’t know. I didn’t know enough English or slang. I had to be told “goes into” means “going into,” and was a familias term for arithmetic. So, the article was titled, “Applied Goes into Arithmetic,” namely Number Theory applied to acoustic diffusion. But the reporter apparently preferred the slangier term, “Applied goes into.” [Laugh]

Sessler:

Now, you talked a little about Number Theory and also some things, relating to fractals and chaos. You wrote books on these topics?

Schroeder:

Ya.

Sessler:

And could you —

Schroeder:

Ya.

Sessler:

— say something. Tell . . .

Schroeder:

The first book I wrote was titled, Number Theory in Science and Communication With Applications in Physics and Communications. This became a very successful book; it was reprinted many times by Springer in Heidelberg.

Sessler:

Fourth, third or fourth printing?

Schroeder:

This is now in its fourth edition, and it still sells like hotcakes. I’m glad that I never listened to any advice, that I wrote the book just as I felt it would be fun to write it. For example, a friend of mine, Henry Pollack, director of mathematics research at Bell Labs encouraged me, to cue it more as a textbook. But I didn’t care about textbooks or trade book. I wrote the book as I liked to write it, and then all the people liked it. I remember one thing I found on the Internet about my book, from a Russian woman, Kristine Lerman, and she wrote, “If I had only one or two books to take to the beach for a weekend it would be Manfred Schroeder’s Number Theory. And, I loved the book except for the corny jokes.” I had her email address and I told her, “Thanks for your nice comments, but what were my corny jokes in this book?” And then she retracted and said, “No, no, there are no corny jokes in the book.” [Laugh]

Sessler:

So, this . . .

Schroeder:

But, there were a lot of puns. I like puns.

Sessler:

This is Number Theory. Now, the other book is Fractal, Chaos, Power Laws?

Schroeder:

Yeah. The other successful book I wrote with a popular slant was called Fractal, Chaos, Power Laws, subtitled Minutes From an Infinite Paradise.” The paradise is an allusion to a statement by Hilbert on Cantor’s Set Theory, which 100 years ago nobody wanted to accept. But Hilbert, the greatest living mathematician at that time, put his stamp of approval on Cantor’s Set Theory with the words, “Nobody will ever drive us away from the paradise of Cantor’s Set Theory.” So, the subtitle is an allusion to that. For example, the famous mathematician Weyl said the Set Theory “Fog on fog,” Poincaré in France also didn’t like it very much. But Hilbert said, “This is a wonderful thing. This is a mathematical paradise.” Incidentally I first wanted the book to be called Minutes From an Infinite Paradise. One reason, of course, is that “minutes” in English has four different meanings. As it is written it – I don’t want to go into it now. And as I said, I like puns. Minutes from an Infinite Paradise. But then the editors at W.H. Freeman in New York, Scientific American, discussed the title and the consensus was that nobody would know what was in the book with such a cryptic title. And so, we compromised. I said, “Okay, let’s call it what’s actually in the book. Fractals, Chaos, and Power Laws, and then the subtitle, Minutes From an Infinite Paradise.” Incidentally, I called it Power Laws, because Power Laws have a lot to do with Fractals and Chaos, with self-similarity as exemplified mathematically by algebraic power laws, as opposed to exponential laws. Another reason why I liked the words “Power Laws” in the title was, again, a pun so to speak. I wanted all the politicians interested in power and all the lawyers interested in the law to buy the book. END SIDE 2, TAPE 1

Schroeder:

A few more things about this Fractals, Chaos and Power Laws book. Again, it was a great delight for me to write it. There are many puns in it. There are many New Yorker cartoons in there that we didn’t even have to pay for them because W.H. Freeman, Jerry Lyons my editor, told me they knew Sydney Harris and these other cartoonists that I was using and they would settle it between the New Yorker magazine and W.H. Freeman. I also had substantial help from my students who provided many of the interesting illustrations. Again, it has a kind of a general audience slant. There are, of course, as in my Number Theory book, a lot of equations. It’s not like Stephen, Stephen Hawking with only one equation, E=MC2. It has a lot of equations, but you can skip the equations. It’s basically, [Laugh] don’t quote me, but good entertainment. And it was very, very successful, and had a fairly high rank at Amazon. And, again I’m very happy with the many good responses that I got from the readers.

But then, just a few years ago I figured you finally should write a book about the real work you did during most of your career, namely speech. And so, I wrote a book, again published by Springer Heidelberg and New York called – I forget right now. [Laugh] Computer Speech. The book was called Computer Speech and the subtitle was Compression, Recognition, and Synthesis of Speech. In other words, voice dialog systems. And, I must admit that I found this much harder to write. This was much more of a scientific book than the other two books I wrote. It wasn’t as much fun for me, especially since I wrote the book about things that I had done in speech five, ten, twenty, thirty, forty years earlier. And, I should have written this book thirty years ago. And, but I felt I had to write a book about my work in speech and so I did it, and as I said it was hard labor rather than fun. But, it too had pretty good acceptance.

Sessler:

Well, let’s talk a little bit about the interaction between you and other people, also the way you learned about, you informed yourself about new developments. What were the important journals for you? Which ones?

Schroeder:

Well I read, of course, Physical Review Letters, because basically I was still very much interested in physics. And, I read the Journal of the Acoustical Society of America. I read the Journal of the Audio Engineering Society. I read the German or European journals on acoustics, Acoustica, and so forth. And, what else do we want to say?

Sessler:

Any books that were of great significance to you?

Schroeder:

I can’t – probably the answer is, there were many books. I can’t recall any right now, and I read very little fiction. Most of the books I read were of some scientific content, but mostly the books I read were about physics in general. Yes, I did work in speech and in concert hall acoustics, acoustics in general, but as I said already I learned these things more by osmosis or as a student, and I read few, if any, books in these fields. But I did read many books in physics, theoretical physics, and so forth.

Sessler:

Yes. And you were in contact with other people working in similar or the same field? (

Schroeder:

Ya. Of course . . .) Was there any conflict ever, conflicting interpretations of results?

Schroeder:

No. No. There were no conflicts. Later when I became a director I had to solve some human relation problems once in a while. For example, we wanted to employ a famous Swedish linguist, Sven, and I asked one of my department heads, Peter Denes, “Take him out for dinner.” And, if the question comes up of whether he had complete freedom to do research at Bell Labs, I told Peter to tell Sven he had complete freedom. And, the next thing we knew is he had hung up posters — this is 1967, the height of the Vietnam War—posters of Ho Chi Minh, Mao Tse-tung, (

Sessler:

Yeah.) and Che Guevara. Then people came running to my office – I never went there to look at the posters. I didn’t want to add to the general commotion. But, people came running to my office, “I can’t do, continue with this classified work with these posters of Mao Tse-tung, and so forth, looking over my shoulder.” I said, “Look, Dave, these posters don’t have ears and they can’t actually see what you write and do.” And, then Bell Labs Security got wind of the situation, as I said big commotion. Had I heard about Mao poster? “Yes,” I said, “I had heard about it,” and I told them that everything was under control, which of course it wasn’t. But, I wanted to get security off my back and I succeeded. Security closed shop on that case, so to speak. Then I called my boss, as was my and others peoples want at Bell Labs you always informed your boss immediately, and I called John Pierce. I said, “Look, so and so has happened and Security has called me, and I told them I will take charge of the situation and it was under control now, and I would do the right thing.” And John Pierce said, “Okay, Manfred. What are you going to do now?” And I said, “John, nothing.” And John Pierce answered with one word, he said “Right.” [Laugh] In other words, we didn’t do a damn thing (

Sessler:

Yes.) and in forty-eight hours the whole situation had blown away and laid to rest, and that was the right way to approach such a problem. To completely ignore it, because minds, after a day or two, will settle down again. I made some very bad decisions too, as a director of research, as when one of our group was on a plane that was in a mid-air collision, between a Pan Am big plane from San Francisco to Idlewild, as it was then known, and a small commuter shuttle from Boston to Newark airport. And, they had collided over Connecticut but the jumbo, although part of the wing was sheared off, was able to make a good landing at Idlewild. But the little plane that, an Eastern Airline shuttle, actually had to make an emergency landing in a potato field in Connecticut and I think there may have been some injuries, maybe even deaths. I don’t recall. Quite a few people reporting to me were on that plane, and I was, of course, eager to find out. We didn’t know yet who had survived. We wanted to know what had happened, who had survived and so forth. And, I made the horrible mistake of calling the wife of one of the “missing people,” whether he was at home. Well, he wasn’t and the wife started crying on the phone and I realized the horrible mistake I’d made. Well, her husband was on the next flight and arrived safely. So, her despair lasted only for an hour or two, but I consider this one terrible mistake I made.

Sessler:

Now, there were no conflicting interpretations of some of the results in the sense, you know, like Theory of Relativity there were immediately some opponents who said, “This could not be true.” or quantum mechanics there were also opponents? Einstein was against quantum mechanics.

Schroeder:

Yeah.

Schroeder:

Well, there were always enough crackpots in the world —

Sessler:

Yeah.

Schroeder:

— who doubted Einstein’s Relativity, or quantum mechanics.

Sessler:

Well, Einstein doubted it.

Schroeder:

Yes. Yes. Einstein had his personal reservations about quantum mechanics. He admired its successes but he always had – quoting from Yiddish, I guess – [Aber es ist nicht a de wahre Jacob] – I don’t want to go into this idiomatic expression but it’s meaning is that “This isn’t the true story. This isn’t a complete story.” Successful? Yes. [Aber es ist nicht de wahre Jacob]. And, he never gave up this standpoint of doubting quantum mechanics, but physics just went past him. And, he was pretty much forgotten. I mean, he turned around in circles in trying to unify general relativity and electromagnetism. And I remember a quote from Wolfgang Pauli who had spent the war years as a Jew, not in Switzerland where he felt unsafe for good, excellent reasons, but at the Institute for Advanced Study in Princeton. And in 1946 they celebrated Einstein’s official retirement from the Institute, and Pauli is supposed to have said, and I think it’s even reproduced in reliable sources, “Herr Einstein, what did you do for physics during the last thirty years?” Of course only Pauli could say such a thing, but it was basically correct that after the famous paper by Einstein, Podolsky, and Rosen, on what we now call entangled states, was really the last noteworthy publication, and between 1935 and his death in April 1956 there was very little forthcoming from him.

Sessler:

Yes.

Schroeder:

Now, you wanted to know whether there are any conflicting . . . Well, I mean, there were different theories of human speech perception and human speech production, and speech learning by babies, and so forth. It’s still a very hot subject and a very interesting subject, and different people sometimes just subscribe to different theories of how we perceive speech and so forth. But, none of these, there were no such controversies as, let’s say, Einstein’s doubting of quantum mechanics or something like that. Yes, there were different theories and different people had different ideas about speech production and speech understanding, but nothing very earthshaking, I would say.

Sessler:

Let’s talk a little bit about things that are more of an advisory nature. You have also served on the advisory bodies on review boards. Could you say something on that?

Schroeder:

Well, I was an associate editor of the Acoustical Society for many years in the ‘60s. I was governor of the Audio Engineering Society, and also an editor for their journal. And, I was on very few government commissions. I was on President Johnson’s Commission for Health Manpower in 1967-68, where we, Dick Garwin and others looked into the problem of the health manpower, asking about the remuneration of nurses and the pay of doctors, and so forth, and the manpower problems that were threatening the American health delivery system as seen in the 1960s. And I think, we prepared a big report for President Johnson. What advice actually he took I don’t know and I hope it had some beneficial effects on the American health system and the manpower. And we should really now say man and woman power, in fact predominately woman power. And so, that was one of the few government commissions I served on.

Sessler:

Yes. During your career you did pure and applied research. You had administrative responsibilities as the director of this center and how was the interaction between all these activities, particularly how did you think about pure and applied science, more mathematically oriented or more practically engineering?

Schroeder:

Well, as I said, we had great freedom at Bell Labs and I certainly promoted it in my area. As I said, Sven could even hang up posters of Mao Tse-tung and so forth. And, I mean, as a general rule the better a person was the more freedom he had to choose what to do. Someone who wasn’t as gifted, perhaps, you had to tell them what to do and hopefully he did it. But, so we had this whole range of freedoms, so to speak, between people who were basically self-motivated and self-directed and some people who needed some direction. And, as I said, not because I was told to but because I felt ethically, so to speak, that I was working for and paid by the telephone company I better do something of interest to the telephone, speech compression as applied by cell phones. And, room acoustics, it connected with Bell’s interest in conference telephony and hands-free telephone, already in the ‘60s. And, but if someone had a good idea in some fallow-lying field – for example, I personally did a lot of work, completely unrelated to acoustics, on computer graphics.

I always liked pictures, images. I was a real shutterbug, won many prizes in photography, and then in the ‘60s I was interested in creating interesting computer graphics in collaboration with Leon Harmon, Ken Knowlton, Mike Noll, Bill Khiier, Bela Julesz and others at Bell Labs. Specifically, I was interested in creating computer graphics that would show completely different things at different viewing distances and one of my computer graphics, titled “One Picture is Worth a Thousand Words,” showing a human eye composed of sixty-five thousand letters that at close inspection shows these letters. From a larger distance shows words, from even larger distances shows the text, which was “One picture is worth a thousand words.” From an even larger viewing distance it would show a kind of a weaving pattern because the sentences were periodically repeated. And then from a very large viewing distance you could see a human eye. I submitted this computer graphic to, in 1969, to the Computer Art Salon competition of the American Society for Computing Machinery in Las Vegas and it won first prize. I even got a thousand dollars for it. Some other computer graphics I sold in Europe. For example, some in Yugoslavia, but they couldn’t transfer the money out of Yugoslavia so I visited them in Zagreb, and the money they gave me was enough for a taxi ride to a fancy restaurant where I had a very good dinner with my wife and our children on our way to Athens for a sailing trip.

So, I didn’t make much money on my computer graphics but that was also a pure delight for me to do visual things in computer graphics. And this was . . . [Tape paused] Now, as I said, this was a hobby of mine and I really liked to do it and I remember one research director’s meeting under Vice President Bill Baker, instead of presenting some research results in room acoustics, in speech compression, or whatever, I just gave a talk, half an hour or so, about computer graphics, the kind of pictures that I had created out of letters or out of thin air, you might say, or pure mathematical equations. And nobody complained. Nobody said, “Look, what are you telling us here? This is none of your business.” No, everybody was interested and delighted to hear my computer graphics story.

Sessler:

Okay, let’s perhaps come back to something we have mentioned before. You said that you met your wife on the third day you arrived here in the United States. Could you tell us a little bit about your wife, her education, her background, how you met her?

Schroeder:

Yeah. My wife was born in Sofia, Bulgaria, and just before the Russians came through Bulgaria. Her parents sent her to a German boarding school in the Black Forest to protect her from the Russians that entered Bulgaria on September 9, 1944. And her father, incidentally, was immediately killed by the Russians, as a capitalist. He was a manager of a large office supply company and always on very friendly relations with his workers, but he was, in their book, a capitalist. And seven days after the Russian occupation he disappeared. He didn’t return from work and nobody knows when he died, either the same day or twenty years later in Siberia, nobody knows. Of course, it was horrible for my mother-in-law for ten, for twenty years. She always waited for news from her husband but it never cames. We all assume now that he was killed, as I said, maybe the same day he didn’t return from work.

So, my wife was now in Germany, separated from the family, and her mother and her sister were still living in Sofia. And, she had some friends in Germany and they made it possible for her to attend a German high school, and she got her abitur there, her school-leaving diploma, equivalent roughly to, as I said before, an American high school plus two year of college maybe. And now she was just on her own. Her family was in Bulgaria, and what to do? Well, she became a displaced person. She came to this country in 1952, sponsored by some American friends, on the troop transport a General Greeley, and then she was sponsored by various friends and churches. She lived in Brooklyn, in Wisconsin, and eventually in New York, where she worked for the Bulgarian desk, after all, she knew English and she knew Bulgarian, the Bulgarian desk of Radio Free Europe. That’s where she worked when I met her. And incidentally, she also spoke fluent German, because even as a kid in Bulgaria her parents had sent her to a German language school where all the instruction was in German. Her governess was Swiss, I believe, at one point, so she learned German from this nanny. And then as I said she went to a German high school. Her German is really perfect, as opposed to 99 out of 100 foreign-born people in Germany.

She’s the only one I know that [Laugh] can speak German faultlessly. I know people who have lived in Germany, Belgians and Americans, and others, for forty years and still make mistakes in German. Of course, it’s a very difficult language. I wrote about, just like Mark Twain, about the idiosyncrasies of Germans the der, die, das business and so forth, which makes it very difficult for a foreigner. But, Anny spoke it perfectly and that was certainly one of the attractions for me, that I immediately had a friend in New York, not only of the opposite sex but well educated, a perfect speaker of German and English. My English, incidentally, was not so good in those first days, and weeks, and months. When I took her out and we wanted to eat steak I ordered a “steek” or two “steeks,” because my English wasn’t that good.

Sessler:

But, in the meantime, or even at that time, you spoke many other languages? I think you are fluent in at least half a dozen languages?

Schroeder:

Yeah. I had gone to Paris for a couple of months to study French at the Alliance Française, Boulevard Raspaille in 1951. Also, in 1951 I attended a summer course given by the University of Pisa in the Collegio Colombo in Viarveggio on the beach where we could swim and at the same time learn a Lingua Cotura Italiana. Italian became, then, one of my favorite languages. I read Don Camilloe Peppone, Boccaccio e Cultura in Italian. I also read Promessi Sposi with some difficulty in Italian. So, I had English, French, and Italian as my . . .

Sessler:

And German, of course?

Schroeder:

German, of course, my native language. And for sheer fun I also studied Dutch. Most of my German friends could speak low German and thus converse, make themselves understood with Dutch-speaking people. But, I don’t know any low German. I only know high German. So, to me Dutch was really like a foreign language. And so, I learned Dutch, as few Germans have, from a grammar book as a bona fide foreign language and the result is I now really know Dutch grammatically and the pronunciation and so forth. And, I always get sick when I go to the Metropolitan Museum and there’s an exhibition of a famous Dutch painter, and the people on the audio tape say – except Philippe De Montebello – the other curators say, “Van Gogh.” [pron. Van Go] Well, who is Van Gogh [pron. Van Go]? Listen to Philippe De Montebello on the audio tapes at the Metropolitan Museum of Art. He says it the right way. It’s Van Gogh [pron. Fun Khokh]. Okay? [Laughter] It’s that simple. Yeah. Not Van Gogh.

Sessler:

Coming back to your family, you have three children, —

Schroeder:

Yes.

Sessler:

— who are all professional people now?

Schroeder:

Yeah. Julian has a named chair at the University of California at San Diego in what’s called molecular plant physiology. He had studied in Germany under Neher, a Nobel Prize winner in physiology. And then being sent on a scholarship to UCLA, and while at UCLA he reads about an opening for an assistant professorship at the University of California in San Diego. He applies and is accepted and pretty soon he was a full professor, then he gets named chair. He got a Presidential Young Investigator Award, and he has already a very successful group. He has a group of some twenty-five postdocs and visitors there, and travels all over the world. I would say that he is really, the only real scientist in the family. He’s really a great scientist. I consider myself just an amateur. [Laugh] You know, I like to do different things, like computer graphics concert halls and speech, but always in a hobby-like sense. But, my son is a real scientist with publications in Nature, and Science, and Proceedings of the National Academy of Sciences, and so forth. Well, more power to him. And, my other son is in San Francisco. He is doing more down-to-earth work there. He’s designing kitchens, and you wouldn’t believe it, there are still many people around in San Francisco and the rest of the country I presume that, building a new house that maybe cost millions of dollars and then they want a kitchen that costs hundreds of thousands of dollars. And Alexander, our second son, is in the business of designing these kitchens. He gets a five percent commission. But considering how expensive these kitchens are, he makes a reasonable living there. [Laugh]

Sessler:

Yes.

Schroeder:

And our daughter, who also studied in Germany, namely medicine, psychiatry, and neurology, is now a practicing physician in Bremen, in Germany. She stayed in Germany while our sons returned to the USA. She does now psychotherapy both for individuals and for groups, group psychotherapy, and she also does expertises for German courts when it comes to responsibility for a crime or drug abuse. But, most of her business is just seeing individual patients in psychotherapy.

Sessler:

Yes. Well, we have to make sure that some records, hard records are kept and so the question is, where are your most valuable primary records? Where can they be found, you know, if somebody is interested in more details on one or the other aspect of your life and your work?

Schroeder:

Well, there is a woman (Margaret Rosen) in Karlsruhe, Germany who is writing a thesis on the history of computer graphics and I’m a prominent subject in her thesis. And, it was through her that I learned that all my papers are, in fact, in existence at AT&T. . . Who is in charge of these archives at AT&T? That’s certainly one primary source. For all my thirty-three years with Bell Laboratories, all my laboratory notebooks and the roughly thirty technical, or more, technical memoranda I wrote, and other things, patents, I have forty United States patents, all these are to be found in the AT&T Archives. And then another source, of course, the University of Gottingen, I think, has in their archives all my publications, and talks, and so forth. So, I think these are two major sources. And so will be the thesis of Margi Rosen, whom I mentioned a moment ago, who is writing this thesis on the history of computer graphics. Let’s see there are . . .

Sessler:

There has been an IEEE interview with you?

Schroeder:

Yes. Another source you might check is the interview I did with Fred Nebeker from the IEEE Oral History Project. There is a one or two-hour interview with Nebeker that’s available on the internet; that contains a lot of information on me both as a person, and as a scientist, and as a hobbyist.

Sessler:

Also you are in the process of writing some memoirs?

Schroeder:

Yes. I always like to find something that’s fun to write about like Number Theory or Fractals and Chaos, and I’m now writing my memoirs and my time as a student, my school years in Germany, my thirty-three years at Bell Labs, my twenty-two years as a professor at Gottingen University, and various other things that have happened to me. One chapter, for example, is Lucky Breaks. That starts when I was just four years old and the infamous Düsseldorf murderer, who had killed many little children, was about to abduct me, and presumably kill me but I had been warned by my aunt – I was visiting her in Düsseldorf – not to follow any man who made some offers of candy or whatever. And so when he talked to me I said, “Look, I’m watching the traffic here. I’m interested in the traffic policeman here,” and so forth, and he could see, this murderer—I later recognized him from photographs—that I had been warned, and he turned around and walked away from me. Then I went home and said, “Aunt, I just met the, Düsseldorf murderer,” Of course she wouldn’t believe it. But then about a month or two later he was caught and his picture was in the newspaper, and yes it was the guy who tried to entice me to go with him. And so, that was my first lucky break.

Sessler:

Lucky escape?

Schroeder:

There are a few more lucky breaks in that chapter, but that was perhaps one of the luckiest breaks. Incidentally, the murderer, Peter Kurten was his name, first confessed to his wife because, believe it or not, he was a kind of a family man. And once he was guillotined, which he was on July 31, 1932, he wanted to be sure that his family had good financial resources. So, he first confessed to his completely unsuspecting wife. Then his wife reported him to the police and she collected the very sizable sum that was made available by the state for his capture. This is peculiar, a mass murderer of children and on the other hand a caring family man.

Sessler:

Huh. Well, I think we have covered most aspects of your life and your work. Looking into the future, is there anything that you, any specific plans that you have for coming years?

Schroeder:

Well, one of my main projects right now, but it’s really just a fun project, is writing my memoirs. Not in any orderly fashion but sort of a random approach. Here I’m writing a chapter about 1930 and there I’m writing a chapter about 1987. Here I’m writing something about linguistics and speech, and mishearings, like Lady Mondegreen, if you know what I’m talking about. The Earl of Murray was killed and they laid him on the green; laid him on the green. And various other linguistic, however. As I said before, I’ve written a long chapter about the idiosyncrasies of the German language. Not unlike Mark Twain, as a foreign speaker, but as a native speaker. And, I find it perhaps even funnier as a native speaker than Mark Twain did as a foreigner, if that’s possible.

Sessler:

Well, I think we come to the end of the interview. There is nothing . . . .

Schroeder:

Well, the only other thing

Sessler:

Yeah.

Schroeder:

I, perhaps I want to mention, I’ve always had a great love of languages. We already mentioned French, Italian, English, German, and Dutch. And I also, at one time in the early 1960s I was quite a proficient speaker of Russian, especially in my pronunciation. I still find Russian easier to pronounce than English, for example. I still have some trouble with some English sounds, like round and wound, or right and white. I find it difficult to make the distinction. But in Russian, I was always…often mistaken as a native Russian. But, then I had to tell them, “Wait a minute. Wait a minute. I don’t follow you. I’m not a native Russian.” I had a real love for the Russian language. A beautiful language. And I remember once at Bell Labs an after-hours course in Russian around 1960. I had to read from a Russian text, Shumachedchi Dow, meaning The Madhouse, written by some dissident, underground writer. And in the middle of my reading to the class the teacher, a native Russian, interrupted me and said, “Class, please listen to Mr. Schroeder. He’s a native German and German, as you know, is a kind of a staccato language. But, listen to him how he reads the Russian just like a native Russian.” Of course, I was in seventh heaven when he said that.

Sessler:

One aspect we haven’t covered, come to think of it is the, your sports activities. There were many sport activities which you pursued during your life?

Schroeder:

Yeah. I was never much interested in sports, and certainly not competitive sports, except tennis. I was a reasonable, not a very good tennis player, and I liked skiing, —

Sessler:

Skiing. Yes.

Schroeder:

— downhill skiing, very fast skiing, too fast really for my ability, and I broke my collarbone once, my shoulder. And then, I very much liked bicycling, and I bicycled all over New England, with, Vermont Bicycle Touring, in Canada. I’ve bicycled on the West Coast, in California, and of course when I lived in Germany about six months every year I bicycled there along the rivers where it wasn’t so steep. I’ve done a lot of bicycling and I always loved it.

Sessler:

Very good. Well, I think we have covered most of the important aspects of your life and work and I think we have come to the end of the interview. Thank you very much for helping us with this interview, for agreeing to answer the questions, and I wish you good luck for the future.

Schroeder:

Well, thank you very much Gerhard. You really squeezed me dry, [Laugh] and, I can’t think of anything I could add at this point. Thank you.

Sessler:

Okay. Thank you very much.