Oral History Transcript — Dr. Tony Embleton
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Interview with Dr. Tony Embleton
Tony Embleton; June 8, 1994
ABSTRACT: Current personal information; Acoustical Society of America membership, committees, activities (1954-1990); mentors Wallace Waterfall, Leo Beranek, R. Bruce Lindsay; family background and early education; Imperial College London (1947-1952); influential teachers George Everington, R. W. B. Stephens; National Research Council of Canada (1952-1990); consultant to the Royal Canadian Mounted Police Chief Firearms Examiner; publications; family, interests and hobbies.
Quirt:What is your present address?
Embleton:I now live at 80 Sheardown Drive in Nobleton, Ontario. This is a small town about 30 miles north of Toronto.
Quirt:What is your present telephone number?
Embleton:It's area code 905-859-1136.
Quirt:Please describe your current employment status.
Embleton:I am now retired. I worked for the National Research Council in Ottawa for 38 years and retired roughly four years ago in June, 1990. Since then I have just done volunteer work especially for Acoustical Society of America, but also for the Institute of Noise Control Engineering and more recently for the International Institute of Noise Control Engineering.
Quirt:How long had you been with the National Research Council of Canada?
Embleton:I had been with the National Research Council of Canada for 38 years continuously, and I was a principal research officer at the time I retired.
Quirt:How would you describe what you did there?
Embleton:The National Research Council is a scientific and engineering research organization and specifically I worked in the physics division on acoustical topics — in particular, things like outdoor sound propagation, microphone calibration techniques and primary microphone standards, and mufflers and silencers. Another important effort was to quieten various types of machinery. I always had the philosophy that the best way of quieting machinery was to design it to run quietly rather than to just put a box around it.
Quirt:What year did you join the ASA?
Embleton:I came to this continent from Britain in late 1952 and applied to join the Acoustical Society almost immediately — within a few months — and my membership with the Acoustical Society was effective January in 1954. At that time I was 25 years old and I considered myself an acoustician. I was in my first job after leaving university.
Quirt:What area of acoustics were you interested in?
Embleton:At that time I was interested in what we today would call physical acoustics. I was dealing with second order effects to do with acoustic radiation forces, the steady forces on an obstacle that can be generated by a sound field.
Quirt:What were your reasons for joining the ASA?
Embleton:At that time the Acoustical Society was clearly the professional society for me, and was also the only one that was of any relevance. There were no Canadian or other American acoustical societies at that time.
Quirt:Was there anyone who encouraged you to join the ASA? If so, who?
Embleton:I can't be completely sure, but almost certainly it would be George Thiessen. At that time the acoustics lab was very small. It just consisted of George Thiessen, Edgar Shaw and two or three technicians, and I was the third professional acoustician to join the group. Both George Thiessen and Edgar Shaw were members at that time.
Quirt:What ASA committees were or are you a member of?
Embleton:I am not currently a member of any ASA committee except ex-officio on the noise committee, but over the years I have been a member of the noise committee on and off for a total of something like 22 years. I have also attended many meetings, though I have never officially been a member of either physical acoustics or engineering acoustics technical committees.
Quirt:What positions in the ASA did you hold or do you presently hold?
Embleton:Oh, I'll probably miss a few, but I feel I've been very fortunate to have done most things over the years in the Acoustical Society. I was the chairman of the noise committee, (technical committee on noise), from 1964 to 1967. After that I was the associate editor for JASA for noise, and that lasted from 1967 to about 1971. Simultaneously with the latter part of that time I was elected to the executive council from roughly 1969-72. A few years later I was vice president of the society from 1976-77, having been vice president elect of course the year before. I was president elect in 1979-1980 and president from 1980-1981. At other times, and I don't remember specific years, I've been a member of the long range planning committee. In fact, I was appointed as one of the first six members as the committee was started. I have served on membership for probably three years. I am currently on the medals and awards committee from I think 1991 onwards, and I know this year I have been reappointed for a further 3-year period, and starting in 1993 and continuing at the present I am the standards director of the Acoustical Society.
Quirt:Is there any particular ASA meeting or meetings that stand out as being something special or humorous or different?
There are. There are so many that are all special in their own way. I thoroughly enjoy most times through most meetings, but I think perhaps one that made a big impression on me was the 25th anniversary meeting in 1954. I remember then there were roughly six head tables, one for editors, one for officers, one for distinguished foreign representatives of other acoustical societies in Europe or from Japan, and in fact almost as many people sitting at head tables as there were sitting at the main floor. The dinner started at around 7 o'clock or some traditional time, and the after dinner ceremonies and entertainment went on until long after midnight. I remember it included an address either in person or tape recorded of all living past presidents of that first period of 25 years. Another memorable meeting was the first joint meeting of the Acoustical Society of America and the Acoustical Society of Japan in Honolulu in 1978.
During the summer, several months before the meeting, I was on my way back from a private visit in Australia coming through Honolulu back to North America, and the person who was to be the technical program chairman, who was at the university but was on contract to the U.S. Navy, suddenly had a sea trip called, and during the critical period of organizing the technical program was out on a ship in the Pacific. A longtime friend of mine was John Burgess, the general chairman of that meeting, and he asked me to serve as the technical program chairman in what was George Curtis' absence. The only inconvenience to me, which was one I was very happy to incur, was to delay my return from Honolulu onwards to North America by three days, the timing was absolutely perfect, and just preside over the technical program organizing meeting. Another meeting that perhaps was a little unusual for me, during the spring 1981 meeting, which was held in Ottawa, I served the society as the general chairman for the meeting and also I was the president of the society at the time. That was the first time that had occurred, but as we learnt this afternoon, Dick Lyon is currently (for this meeting at MIT) also the president of the society and the general chairman of the meeting. That is the second time that this coincidence has occurred. It's a rare event, and it's a lot of work, but very enjoyable.
Quirt:Were there any ASA members who you met who especially influenced your future?
There are very many who gave mentorship and advice. Sometimes I have had to ask for the advice; sometimes people have come to my, shall we say rescue when I got myself in hot water, and I am very appreciative of many of these. In fact, I feel very privileged to have known and have benefited from almost all the people I can think of through my lifetime who have been great acousticians. Obviously I never had any connection with people like Lord Raleigh and Stokes and other people of the last century long before I was born, but I particularly remember Wallace Waterfall, the longtime secretary of the society who for many years was a very good advisor and mentor. Those of us who knew Wallace Waterfall would realize that he had a special personality that was never pushy; he was always there and always available, but always in the background until someone needed help, and then he would give you all the help and advice he possibly could.
Another person that I feel that I owe a lot to was Leo Beranek, who was at that time a professor at MIT and also the head of a very successful consulting firm, Bolt, Beranek and Newman. And my connection with Leo Beranek came about through the MIT summer courses in acoustics which were held every two or three years through the late 1960s and on into the early 1970s. Leo Beranek was the organizer of the meeting, he arranged the curriculum and many of the other details interfacing with MIT, and I was the co-director of the course. The rough arrangement of those courses was that Leo Beranek taught every morning or almost every morning, and I taught whatever else was required almost every afternoon through a 2-week course. And then there were a number of other people, 10 or 12 other people, drawn mainly either from Bolt, Beranek and Newman or MIT, who would each teach an hour or two on specialist topics.
The afternoons were very interesting. They were a mixture that one responded to in an ad hoc way each day. There were questions and answers to fill in, dealing with people's problems if they had any or didn't understand the morning lectures, there were tutorials to smaller groups, perhaps on architectural acoustics things or underwater acoustics things, vibration projects, and there were either demonstrations or lab experiments that people did. A real mixture of work with a very large number of people. We had usually something like 150 to 180 students. Another person that I particularly remember — all these people with great respect and great affection — was Bruce Lindsay, a towering figure in acoustics and a longtime editor of Jasa. And in fact I remember one very memorable breakfast at a meeting in Miami when Bruce Lindsay and Hallowell Davis were sitting down having breakfast together. I came into the dining room alone, and they beckoned me over to join them. These two great figures in acoustics talked, and my role was one of spellbound listener — they were both about 80 years old and I was around 45. And I remember particularly Bruce Lindsay saying that when he was a small boy, I think something like 3 or 4 years old, Lord Kelvin visited Bruce's father, and Bruce went in and saw the great man and full of excitement said, "Guess what? I was born on the first day of this century." Bruce's birthday was January the 1st, 1900. And Lord Kelvin, who obviously was not too familiar with little boys and how to encourage them and humor them said, "You were not born on the first day of the new century. The first day of the new century is January the 1st, 1901. You have to complete the hundred years to make a century." Bruce remembers the story, and it doesn't seem to have turned him away from science.
Quirt:Is there anything you would care to say about the ASA, past, present or future?
Embleton:Yes, many things, and perhaps I can summarize them by saying that I feel it is one of the most friendly professional organizations that one could ever wish to belong to. I think that this is because it is mainly a volunteer effort, very few permanent staff, and everybody does what they can for what they see as the common good of all acousticians. Each of us as individuals realize that almost everybody else at meetings is also a volunteer, and it makes one feel almost as though it's a privilege to belong and want to do things for the society. I think perhaps another factor which relates to a relatively small number of us, and I feel very privileged to be one of these people, but I have been fortunate enough to have been honored with two major awards from the society. As a young acoustician I received what was then the Biennial Award, but which is now known as the Bruce Lindsay Award, and more recently I received the Silver Medal in Noise. I think that was probably in 1988 or thereabouts. And this just increases my sense of loyalty and duty and desire to serve the society in every way I can. And of course not just the society, but one indirectly serves all the members, and it's a great society to belong to. I don't have this feeling about any other society, and talking to people occasionally about this sort of thing I don't think many people have this feeling for many other societies either, but we all seem to share this sentiment about the Acoustical Society.
Quirt:Besides ASA, what other professional organizations do you belong to?
Embleton:I belong to INCE USA, Institute of Noise Control Engineering of the USA, and I'm also a member of the Canadian Acoustical Association, which is a much smaller but otherwise perhaps similar acoustical association in Canada and which I believe started in about 1961. It is a much younger organization also. I belong to other societies as well, but they are not professional in exactly the same way. I'm a Fellow of the Royal Society of Canada, to which one is elected. It's an honorary society. Of that I have been an officer — I was treasurer for three years from 1982 to 1985. And I'm also a foreign associate of the National Academy of Engineering, to which I was elected I believe in 1978. There are about 100 foreign associates spread around the world out of a membership of something like 1600-1800, and of those foreign associates about 10 or 12 are in Canada.
Quirt:We'll now discuss past history beginning with your early years before college. When and where were you born?
Embleton:That is a good place to start. I was born in Hornchurch in Essex in England. Essex is the county bordering London to the north and east, and Hornchurch is a small town which at that time was more or less in the country, about 20 miles east of London. Since then London has grown and has absorbed Hornchurch. It is now just a suburb. I was born on October the 1st, 1929, and I often like to think of that as the same year that the Acoustical Society of America was born.
Quirt:Before entering college, what were some of the places you had lived?
Embleton:I really only lived in the one place. I had always lived in Hornchurch, and so I lived there from 1929 until 1952, when I came to North America.
Quirt:What were your parents' occupations?
Embleton:My father was managing director of his own firm. The firm was in fact founded by his father, and the company's business was trading with India and Ceylon in such products as coconuts and coconut fiber for making mats. Occasionally the company would trade in other commodities, such as nails or other small manufactured goods. My mother had been a bank clerk before I was born, but at that time she retired from work and did not work again. During those early years I was an only child and I felt that I was very well looked after, I felt very comfortable, very secure in the family unit, and as I grew up I went to a private boys' school for all my elementary and high school years. That is a private school in the North American sense. It is what the English would call a public school.
Quirt:As a youngster, what did you want to be when you grew up?
Embleton:As far as I can remember, I had no particular ideas as to what I wanted to be beyond something that was professional, technological and reasonably precise in the sense of science or mathematical precision. Before college I had a number of hobbies, but I should perhaps preface these comments by saying that I grew up just east of London during the Second World War. I was about 9 years old when the war started, and I was 15˝ when it ended, and so I grew up as a young teenager in wartime years. One's hobbies to some extent were curtailed, and so my hobbies were such things as collecting stamps — which keeps you fairly close to home. I have to say that another hobby was, collecting the debris of war, whether it was shrapnel from anti-aircraft shells or cutting bits of metal off downed German fighters, and things like that. And possibly, what heros did I have at that time? I think perhaps in common with almost everybody else in Britain my hero, my great hero, was Winston Churchill, who rallied the nation at that time.
Quirt:What subjects, events and activities did you enjoy most at that stage in school?
Embleton:As far as subjects were concerned, well, many subjects, particularly math, physics, chemistry, but also some art subjects such as Latin and French and geography. The things I liked least were English, especially English literature, and history. I took part in a number of school sports. I played football in the sense of English soccer, I swam, I played on the school chess team, I played squash, and I guess that's about all. In one or two subjects I was reasonably good. In Latin for example I at one time had a better gut feeling for the structure and nuances of the language than I think I did in English, and could quite easily and happily carry on a conversation or a discussion in Latin. I have lost that skill through inaction over the last 50-odd years.
Quirt:Looking back, was there any person or persons during that period who had a strong influence on you and your future?
Embleton:I think probably given the direction my future career took, the most influential person was my senior math teacher, who was a gentleman by the name of George Everington. He was a fascinating man and he was an absolutely excellent teacher. He was fascinating because he had been a navigation officer on one of the British battleships at the Battle of Jutland in the First World War. I guess being a navigation officer is a mathematically related subject, and anyhow, for whatever reasons, he was able to put the subject together as a coherent whole. That was the way he taught. He didn't just teach you things as facts; he taught you to think, put the structure together, and if you couldn't do something, to work from more basic principles, and develop the analysis in work the way you wanted to go. So apart from giving me an excellent knowledge and fluency in mathematics, he also taught me how to use my mind and face problems of unknown solution. He did not teach math by rules. You just got to understand what it was all about, and you could work almost anything out that you wanted to, even if you'd never seen it before. And I have to say that when I left school and went to university, I did math courses at university but I did not really learn anything new at university that I did not already take, so to speak, with me from high school.
Quirt:Moving now to college years at the undergraduate level, where did you first go to college and what was your major?
Embleton:I went to college at Imperial College London, which is one of the major constituent colleges of the University of London. Went into the physics department in 1947.
Quirt:What made you choose that college and that major?
Embleton:I chose that college because in the circumstances of the time in 1947 there were very few university entrance places for people going directly from high school. Ex-servicemen had preference over people going directly from school, and there were many ex-servicemen who were availing themselves of the opportunity to go to university. It happened that there were a series of scholarships called Royal Scholarships which were funded from the proceeds of the Great Exhibition in London in 1851, and these were tied to Imperial College, and so I chose to take the rigorous exams for the Royal Scholarships, and if successful one was guaranteed a place in the university in Imperial College. The competition was very great. There were rigorous written exams. I happened to know that there were 20 scholarships awarded out of 1850 applicants, and I came first in the mathematical and physical sciences part of the competition.
Quirt:As an undergraduate, did you ever change college or major?
Embleton:No, I did not change. I did my undergraduate and in fact graduate training at Imperial College.
Quirt:As an undergraduate, did you belong to any special clubs or participate in any special school activities?
Embleton:Yes. I was president of the college Mathematical and Physical Society for one year in about 1950 and as far as sports were concerned I was on the rowing team as a member representing the college for four years and I occasionally, (not exactly sports but other activities), would fill vacancies if they occurred on either the chess or the field hockey teams and I believe on one occasion on the college squash team.
Quirt:After that pause, would you please tell us about your undergraduate college days? Was there any particular person, teacher, professor or someone special who had a strong influence on you or your future?
Embleton:I think that the person at college who had the greatest influence on me was R. W. B. Stephens, Ray Stephens, and known to staff and students alike as Steve. He was not only a lecturer of undergraduate courses, but he also had responsibility for the acoustics group at the graduate level.
Quirt:During that period of life, who was your inspirational model?
Embleton:I don't think I could name anybody as an inspirational model. There was, as I say, Ray Stephens who was a thoroughly nice, gentlemanly person who really cared for students attracted me into his acoustics group, but I don't think that anyone else particularly comes to mind.
Quirt:Did you ever participate in a rally or a protest or a cause? And if so, what was the issue?
Embleton:No, most certainly not. No issue and no cause. In fact I think philosophically I am strongly opposed to any idea of pressure groups, or single interest groups or activists. I feel that they are a distortion of our democratic process. I think one has to go through the process of electing representatives, maybe not a perfect system, but I think it's very much better than having a fragmented lot of activists where the one who shouts loudest gets his way. I think we have to go with obviously a package deal covering many issues. In the policies of any particular, shall we say, political party very often one likes some, dislikes others, but on balance one has to go for the party that one if anything dislikes least.
Quirt:Looking back, would you go to the same college and take the same major if you could start all over again?
Embleton:Yes, I certainly would. Imperial College at the University of London was, and to some extent perhaps still is the major technological institution in the country. Since I left the University of London or left Britain, the Institute of Sound and Vibration Research at Southampton has come into prominence. It didn't even exist when I was there, and has become a major force in acoustics; also there are some very good research groups at a number of other British universities — Birmingham, Manchester, and several others that I forget for the moment. But none of those existed at that time. So I think given the circumstances at the time certainly I would go back to Imperial College and do things more or less the same way again.
Quirt:At the graduate level, did you go to graduate training?
Embleton:I did, and I stayed on at Imperial College. There was a particular reason for that. I got my undergraduate degree, my Bachelor's degree, in two years. That is to say, I did all the course work and earned it, but there was a University of London regulation that you had to spend three years. So I stayed on at the college for the third year in order to get my Bachelor's degree, and if I had to stay there I might as well do something useful, so I started on my graduate program towards a Ph.D.
Quirt:You went directly to a Ph.D. without an intervening Master's?
Embleton:Yes, I did. At that time Master's degrees were offered, but in general one tended to work towards a Ph.D. Only if one had to cut short one's studies or for some other reason things didn't work out, then one would often have enough work completed to earn a Master's degree. But the Master's degree really was the second option if the Ph.D. did not work out in some way.
Quirt:You've already explained one reason for your choice of school and curriculum. Were there other reasons for your choice?
Embleton:Other reasons. Not particularly. I think that the Royal Scholarship was certainly the dominant reason, and perhaps as far as I can remember now the only reason. But it also had the advantage, given the amount of property that had been destroyed through bombing in the Second World War, that university residences were very scarce and by going to the University of London I was able to live at home and commute. It was about an hour to an hour and a half each way each day, but one could do a certain amount of reading on the train.
Quirt:How were you supported? Did you have a job?
Embleton:No, I did not have a job, and only once during my graduate years did I have even a summer job. By and large I existed on the Royal Scholarship that we mentioned earlier. That supported me through my undergraduate years, and for the first year of my graduate work, a total of three years. Thereafter I held a University of London Postgraduate Scholarship for two years, which was enough to see me through to the end. The reason for changing was basically that the University of London Postgraduate Scholarship was worth about two and a half to three times as much money.
Quirt:Were there specific projects that you worked on?
Embleton:The specific research project that I worked on (which became the subject of my Ph.D.) was the nonlinear distortion of large amplitude pulses. In those days one had to build all one's own equipment, and it was also in the days before transistors and other devices so one relied on vacuum tube technology. I measured these large amplitude pulses which propagated one dimensionally down a shock tube with glass windows at the side by means of a Mach-Zehnder interferometer, which was an optical interferometer in which it was possible to separate the two interfering paths by a very large distance. The Germans had used these previously to put the reference light beam around the outside of a wind tunnel and pass the measuring light beam through the wind tunnel. One could have path lengths of something like 20 feet and path separations of 8 or 10 feet. I built my own obviously much smaller Mach-Zehnder interferometer, including the mountings for the optical flats, grinding the optical flats myself, and their adjustment mechanisms that I constructed myself. The system formed an interference fringe over a narrow slit of the order of a thousandth of an inch wide, and this slit was in front of a photomultiplier tube. I, in fact, used one of the first 10 prototype photomultiplier tubes ever built in Britain. It was a loan from the company. That was another one of Ray Stephens' skills, he could scrounge equipment from almost anybody and we ran the research group on very little money.
Quirt:You've mentioned Ray Stephens. Are there other things about Ray Stephens that had great influence on your future, or are there other people at the school who had a great influence on your future?
Embleton:I think that Ray Stephens was overwhelmingly the one person who had a positive and attractive effect on my future. Perhaps I should not go into it, but there are one or two others that so to speak pushed in the same direction, but mainly because they were repelling me from certain other areas of activity.
Quirt:Moving to other academic activities, while you were a student, did you ever conduct any classes for the college?
Embleton:I never conducted classes at the college. I occasionally would work as a teaching assistant in an undergraduate lab for very little, and possibly zero remuneration. I did do a bit of teaching at some of the technical schools associated with the University of London, and there I was teaching quite elementary level courses in general acoustics — usually evening courses. One of those I remember was in west London, Acton Polytechnic as it was at that time, but another one was more in the center of the City of London, but I do not remember its the name now.
Quirt:Moving to other training issues, did you have specific experience in the military?
Embleton:No. I never served in the military at that time, when I was of the order of 20 years old. I was exempt, and then following that, almost immediately upon getting my Ph.D. I came to Canada on a postdoctoral fellowship. Perhaps I atoned for that in later years by serving as the Canadian representative on NATO scientific committees. That was much later. In fact, I served as far as I remember from either 1982 or 1983 until 1990. By then I had some acoustical knowledge and knowledge in peripheral areas and was able to contribute as a technical expert.
Quirt:Did you ever attend, or were you involved in any technical, business or trade school?
Embleton:None. I certainly did not attend any, and as I just said, I did teach part of an acoustic course at two of the technical schools associated with the University of London and in the London area. And those courses that I taught were in acoustics.
Quirt:Did you ever take any correspondence courses?
Embleton:No, none. I guess I really took very few formal courses in acoustics either at the university or through correspondence. Most of it I picked up by osmosis.
Quirt:After college, what was your first place of employment, your first title, and what did you do there?
After I left college I went to the National Research Council in Ottawa as a postdoctoral fellow arriving in November of 1952. That was not only my first place of employment but has been my only place of employment. The postdoctorate fellowship lasted until the end of 1953. After that I joined the regular staff and rose through the ranks. I started as an assistant research officer in early 1954 to 1957. Then I became an associate research officer January 1958 to the middle of 1962, then senior research officer from July 1962 to June 1974, and thereafter as a principal research officer from July 1974 until my retirement in 1990. In those later years I was head first of the acoustic section and then when there was a bit of a reorganization and two sections were amalgamated, I was the head both of acoustics and the mechanical standards work, which involved the primary standards of mass and the related standards for pressure and density.
What did I do there, any special projects — I worked on quite a wide range of things. I worked on second order acoustical phenomena, acoustic radiation forces which are the steady forces that are exerted on an obstacle as a result of a sound field, and in particular my area of work was when the sound field was not plane; in other words, say near to a point source or near to a line source. There are many interesting things that can occur there. The direction of the forces can change in a very systematic way, which depends on size of the obstacle, distance, frequency, and so on. In a more applied area, I did some work on quietening of paper making machinery. The suction rolls in paper mills are particularly noisy, they can cause hearing loss from prolonged exposure over a working lifetime. There we utilized the philosophy that we've always held about quietening machinery by redesigning the machine. These rolls made their noise primarily by a siren-like action from a multiple array of sirens, and we arranged the phasing between the adjacent sirens in the array so that there was destructive interference between them, but destructive interference in such a way that it just did not shift the direction of maximum radiation to another direction. It shifted in fact right round sort of to an end-fire position and then contracted it. In that way we achieved about 12 decibels in practice that theoretically should have been a reduction of about 50 decibels, but that's the difference between theory and practice. But 12 decibels, by redesigning the machine, was very effective over the years since we instituted that.
The gain that we achieved then by reducing the sound level has largely been lost because machines now run much faster than before and of course make increasing noise with increasing speed. And so the net effect over a period of maybe 20 or 30 years has been that paper mills are now about twice as productive, but for no more noise. I did quite a bit of work in other areas at different times in developing silencers — either metal silencers for various pieces of machinery, or, in one interesting case, designing and testing silencers for air-driven jackhammers. There one has the interesting possibility that because these devices are air-driven you do not have hot exhaust gases to cope with and you can use plastic moldings. You can make plastic moldings in much more complex and different shapes than if you are making a muffler by welding together pipes and plates. And so there are other possibilities of building in, in a cooperative way, and silencing mechanisms by a number of different routes — plates of varying hole sizes for example, that act to reduce large amplitude waves by nonlinear processes as well as the conventional pipes, cavities and so on that are used or and are known to be effective in small amplitude linear acoustics.
I also for a while developed improved methods for microphone calibration, which meant that one could calibrate primary microphones something like 10 times as precisely as formerly. In other words, to an accuracy of perhaps three hundredths of a decibel instead of one or two tenths of a decibel. A major area of work in my later years was in the area of sound propagation outdoors. That was largely uncharted territory when I started on that in probably about the mid-1970s, but bit by bit one unraveled the special effects of finite impedance ground, the ability of ground to acoustically support surface waves, (trapped surface waves traveling in the air above the ground) and how to recognize and quantify disturbances to the measurements by either refraction due to vertical gradients of wind and temperature in the atmosphere, or the scrambling of phase relationships by propagation through atmospheric turbulence. These phenomena all interact, and depending on circumstances some can be dominant, others not so dominant, but it makes for a very complex, very interesting situation.
It enables one to explain the work of others, as we were able to do, that appeared to be totally contradictory. For example, in motor vehicle testing, the propagation distances were of the order of 50 feet over hard concrete or asphalt surfaces, whereas for some measurements, perhaps particularly of aircraft noise or just general environmental community noise, one is interested in much greater distances of propagation over what are predominantly soft or semi-soft, that is low impedance ground surfaces, typically grass, sometimes snow. So we were instrumental in working at the core of that subject and making it possible to get a coherent picture of outdoor sound propagation even though most of the measurements, very good measurements made very precisely in a number of other labs, dealt with specific areas of the subject.
Quirt:Was there anyone there who had a particular influence on you?
Embleton:I think one has to say most especially George Thiessen, who was our longtime section head for many years. He had the right kind of personality that held us all together, understood our problems, and was to some extent a general father figure to all of us. A number of my other colleagues, acousticians, also had greater or lesser influence on me and sometimes more at some times than others, because our group worked very well together. Often we worked as individuals; other times we worked in particular collaborations of two or three of us on particular projects and then went our own ways again for a few years. And so in particular I must mention over many years Edgar Shaw and Joe Piercy and in more recent years new recruits to the section, people like Gilles Daigle who, on my retirement, took over the section as section head, and Mike Stinson. Other people joined about the time I left, are still working there and are faithful members of the Acoustical Society today — Dave Havelock comes immediately to mind, and George Wong.
Quirt:You have mentioned that you stayed there for 38 years. What year did you leave?
Embleton:I left in June of 1990. At that time I was at the top of the grades that one could hold as a professional working scientist and engineer, in other words nonadministrative rank. I was at the top of the principal research officer grade, and the position I had in the council was, head of the acoustic section, which is of primary interest to us here of course, but also of the mechanical standards section, which was primarily the National Standards Laboratory for mass and the derived quantities of density and pressure.
Quirt:Why did you leave?
Embleton:I left for, well, I guess several reasons. Maybe some people would say 38 years in one place was enough, but I had always had a long term goal to retire early. That probably became a goal which formulated almost during my college years, or as soon as I started work in my mid-twenties. The general idea was that I wanted to retire early enough to do other things, whatever they were — hobbies, travelling, and so on, while I still enjoyed health that was good enough to do it. Obviously once one gets into one's sixties or presumably even more so later, one's health tends to be a monotonic function heading downwards, and so as a general principle it was better to retire earlier rather than later. I also had the intention that I would want to keep in touch with acoustics, and so whilst not actively engaged in research anymore in retirement — especially as I've moved away about 300 miles from the original lab — I continue to work on a volunteer basis, especially for the Acoustical Society of America, but also for INCE USA (Institute of Noise Control Engineering) and more recently for the International Institute of Noise Control Engineering. These are volunteer things, and I do them because it keeps me in touch with all my professional friends and colleagues of many, many years, and, as I said earlier on, because I feel a great sense of loyalty and duty to the Acoustical Society.
Quirt:Moving now to the topic of publications, did you ever write a book or contribute to a book?
Embleton:I have never written a book on my own. I have contributed to several books, and I wrote two book chapters in one of Leo Beranek's books, which was published about 1970. One chapter was on sound in large enclosures, which if you like were rooms typically in buildings, and the other chapter was on mufflers, silencers, sort of things that you can put on machinery or automobiles, that type of thing. Later on I wrote in collaboration with Joe Piercy a chapter on sound propagation in a book that was edited by Cyril Harris, and more recently in a book under the auspices of AIAA Society that was edited by Harvey Hubbard. Again that was on outdoor sound propagation. Those are not the exact titles, but that's certainly the subject. In addition to that, I've published something like 50 papers in JASA, one or two letters in JASA. I've also published one or two papers elsewhere. I have one for example in the Chinese Journal of Physics or Journal of Acoustics, which was the result of giving a lecture in Beijing in 1987, but most of the publications have been in JASA. I also have one or two patents.
Quirt:Speaking of your JASA publications, is there any one of which you are particularly proud?
Embleton:I think several of them have been very useful. One of the earlier papers on sound propagation outdoors was not solicited as a review paper in the sense that we have the review and tutorial papers but was very much a review paper in nature, and that has been referred to by quite a number of people. I think that was a very important paper. I think, funnily enough, one of the more useful things that I published in JASA was a 1-page, probably even less than 1-page, letter to the editor which sorted out the sound propagation literature into the two categories of those authors who had based their theories on e to the plus i Omega t time dependence and those that had used e to the minus i Omega T as the time dependence. This was important because this distinction carries through to the signs that are used, both for propagation distance and also for impedance, or at least the complex part of the impedance — whether something is capacitative or inductive. That has been very useful, even for people working in other organizations; for example the SAE A-21 aircraft committee, where the chairman chose to make reprints of that paper and hand them out to all members of his committee some years ago.
Quirt:Moving now to issues of family, what is your present marital status?
Embleton:I have been married for 41 years to Eileen. Before we were married, and to some extent for a while afterwards, Eileen herself is a chemist. She has a Ph.D. from the University of London also, but from a different college. After she gave up teaching or work for a few years when our daughter was born, she taught subsequently for some years at the University of Ottawa. We have one daughter, and she as a linguist does have some marginal connection with acoustics, though as her career develops she is shifting away from that. She has in fact attended one or two ASA meetings and her interests or her connection at that time was in acoustical phonetics, and by training she has a double major. In fact she has both a Bachelor's degree and a Master's degree, B.Sc. and M.Sc. in math and linguistics. The Master's degree is more specifically in statistics, but her Ph.D. is in linguistics. She applies this combined knowledge to mathematical models of languages, especially the sort of language tree of we'll say Indo-European or North American Indian languages where mathematical analysis, statistical analysis of the language structure in all its aspects (spoken, grammatical, and written) can provide clues as to the interrelationship between languages. Two languages that are very similar today parted company not many years ago, two languages that are very different today may have parted company 5,000 or 10,000 years ago. These models can be tested against known historical evidence and validated, and then can be used, but without validation to prehistory.
Quirt:Where and when did you meet your spouse?
Embleton:As I said, my spouse was at a different college of the University of London, University College, and I was at Imperial College. We met by chance, both taking a Russian course, having chosen to take a Russian course quite independently at another school at the University of London, the School of Oriental and Eastern European Studies. We were not particularly attracted or noticed each other at the beginning of the course, there were about 40 people in the class, but as the year progressed people dropped out for one reason or another — either they didn't have the time or Russian was too difficult — and for the last one or two lectures towards the end of the academic year the room had only four people in it: the lady who was going to become my wife, though we were not engaged or anything at that time; the wife of the chairman of my wife's department; and the Russian teacher himself. So I guess, as the only two young ones in the room, we were drawn towards each other. That was in London, but we in fact did not even get engaged until almost a year later, when Eileen had come on a Fulbright Fellowship to Cornell University — which as we know is in New York State — and I went on my postdoctoral fellowship to Ottawa. And so being only about 250 miles apart, we did decide to meet from time to time, and things developed from that. We were married in Ottawa about a year later, and in fact our reception was held in George Thiessen's home.
Quirt:I think that covers all the family questions.
Embleton:Right, I think so.
Quirt:Other personal interests. What is your favorite form of entertainment?
Embleton:My favorite form of entertainment these days, apart from looking after and trying to guide and help my granddaughter, who lives with us part of the time — because both her parents work full time — is gardening, and in the winter, when there's no gardening, I get my exercise shoveling snow. I do not have any mechanical devices, I just have my arms and a shovel. So I get my exercise, and I really quite enjoy snow shoveling. As for entertainment and hobbies, I still retain my interest in stamp collecting, and I do not, as some people do, collect stamps as a financial investment. That is of no interest to me at all. I collect stamps because I like stamps, and I collect anything that can come my way.
Quirt:Could you comment on favorite authors or types of books?
Embleton:I read to some extent, but not as much as many people. I definitely prefer nonfiction books, and preferably biographical books of well-known figures or interesting figures — people perhaps like Winston Churchill, perhaps in the sense of spy stories on outstanding spy masters, or the story of how some codes were broken in the Second World War and things of that type. Other favorite things in the artistic area, so to speak, as far as movies are concerned, I either watch them when they finally get around to being shown on television or occasionally go to very selected movies. We very rarely go to the movies. And the last probably two movies that we went to, and we're going back a few years now, that made an impression on me, were Man for All Seasons and Ghandi. So you can probably say that I probably haven't been inside a movie theater for about five years.
Quirt:In more popular culture, do you have any particular interests in music, singers, TV programs, sports teams?
Embleton:Not particularly. I do not play an instrument myself or sing. In terms of music I like light or medium sort of stuff, not modern rock and roll or jazz stuff. At the other extreme I would tolerate but I don't particularly enjoy symphonies, but something a little lighter than symphonies suits me extremely well. No particular favorites, composers or otherwise, but I enjoy a reasonably wide range of things of the right type. On TV programs, I particularly enjoy documentary programs of most types, and also the various British series that one can see either on PBS network here in the States or our equivalent on TVO, Television Ontario in Canada. In fact we are particularly lucky, because we are able to receive both of those very well, and they tend to show a similar class of program material. I have no great interest in sports. I will occasionally watch baseball games on television, and in fact I have even been known to watch one or two major league games live, but one in about 20 years doesn't really class me as a great fan.
Quirt:Any interest in art?
Embleton:I enjoy looking at art, looking at pictures. It is really just at the level of an enjoyment of art, especially the old masters, the impressionists, and some modern artists. Ido not enjoy impressionistic or other outrageous styles that are apparently the vogue today.
Quirt:Is there any specific quote that strikes your fancy?
Embleton:Nothing particularly comes to mind. I suppose if I thought about it there are several quotes that occur to me from time to time, depending on activities, but nothing that I would really want to mention at this point.
Quirt:What are your future plans?
Embleton:Really to carry on pretty well with the things I am doing now — spending more time with my family and to the extent that I can, providing logistical support, whether that's chauffeuring or baby-sitting or whatever to my family, who are very productive members of society and of course are younger and have much more stamina. I'm happy to continue my volunteer work for the Acoustical Society and for INCE for a few more years, but, depending on health — not that there's anything looming at the moment — I will probably aim to gradually work my way out of these things, hopefully passing on some skills and advice to younger people.
Quirt:I there anything else that you'd like to add?
I think that I would just like to make one small comment, and that is that for quite a number of years I've done a variety of things that in fact I have found very interesting (more interesting almost than my published work) in various applied areas that has never resulted in publications or recognition. These were the best things, because for example working on certain military problems or intelligence problems, one knew that whatever one did that was innovative or unusual would be taken away by onne's client, used immediately, and was serving a great need. One got the feeling that one was really making a contribution, because one was applying one's skills to unique problems, skills that perhaps couldn't be obtained elsewhere and, for the people who were using them at least, were extremely valuable. Another thing also, a little more overt, was that I became an expert on gun silencers.
The national police force in Canada is the Royal Canadian Mounted Police, and they run the National Crime Detection Laboratory, and one of their senior officers has the glorious title of "chief firearms examiner" for Canada. On acoustical problems I became his chief, in fact only, acoustical consultant. My evidence in various interesting court cases has ranged all the way from probably securing the conviction of someone who got about 5 to 10 years in jail to my evidence completely exonerating the person because it caused the Crown's case against him to collapse. For four or five others there were results that ended in between.
This concludes the taped interview.