Acoustical Society of America
Biennial Award - 1976

Robert E. Apfel

Robert Edmund Apfel was born in New York City on 16 March 1943. He received the A.B. (Magna cum Laude) in physics in 1964 from Tufts, and the A.M. and Ph.D. in applied physics from Harvard in 1967 and 1970, respectively. He is currently Associate Professor in the Department of Engineering and Applied Science at Yale University.

Bob's interest in acoustics began while he was at Tufts where he undertook and completed a senior honors project on auditorium acoustics using equipment borrowed from Harvard, MIT, and BB&N. Thus, when he became a graduate student at Harvard under the late Professor F.V. Hunt, he was already experienced in the sine qua non of experimental research—where and how to scrounge equipment. The culmination of Bob's graduate work was a thesis on vapor cavity formation in liquids. Among other things, he measured for the first time the intrinsicstrength of a liquid; that is, the strength in the absence of adventitious defects. A liquid can be cleaned by filtration to a degree such that the probability of some sample of it having no defect can be made nearly unity by making the sample sufficiently small, in his case a droplet of some tenths of a millimeter in diameter. An arrangement based on this notion, combined with the technique of levitation of the droplet in a host liquid sustaining a cylindrical standing wave, enabled him to procure cavitation in the droplet by adjustment of the temperature and acoustic pressure. As a result of Bob's labors, we have now at hand a tool for the study of the liquid state analogous to the use of whiskers in the solid state. The results of this work are in good agreement with theories of homogeneous nucleation and give us some confidence in our perception of the liquid state. Not content with that, Bob fleshed out his thesis with important contributions to the theory of heterogeneous nucleation, which help establish a framework within which the previously troubling vagaries of experimental date on acoustic cavitation can be better apprehended.

The results of Bob's graduate work were communicated in a series of papers in our Journal and others and won him instant recognition. Although the job market was tight when he left Harvard, he had four firm offers of employment, one unsolicited. He chose to go to Yale as Assistant Professor in 1971 and was promoted in his present rank in 1974. In 1971, also, he was awarded the A.B. Wood Medal and Prize by the Institute of Physics and the Physical Society of London. This was the second of these awards, which are restricted to the young.

At Yale, Bob has continued to exploit his technique, applying successively more ingenious and innovative experimental methods to increasingly complex problems of metastable liquids. He finds time, nevertheless, to indulge his boundless curiosity by investigating more esoteric (far out) matters. An example is decompression sickness in mice. (Sounds reasonable.) Bob is regarded as an outstanding teacher. In order to accomplish his mission at Yale he has developed some new courses—Physical Acoustics, Architectural Acoustics, and Environmental Acoustics. He is the only junior faculty member on a team which teaches a series in "Perspectives on Technology." His section, on acoustics, especially some reproduction, has attracted 420 undergraduates in two years. He participates in Summer Research Programs for undergraduates and works with high-school science students. On the side, Bob manages to do some consulting in noise and environmental acoustics.

Apfel is a devoted member of the Acoustical Society. He has been to every meeting but one beginning a year before graduation and has read a paper at each of nine of them, at least. (Not to mention a paper at each of two ICA's.) He serves on our Physical Acoustics Committee and on the Committee on Education in Acoustics. In connection with the latter he has prepared two review articles, "Acoustic Surface Waves in Piezoelectric Materials—A New Technology" and "Perspectives on Occupational Hearing Loss."

Science is not all. Bob goes for tennis, theater, and music (he sings). And that's not all he goes for, as is tolerably obvious to anyone who has met his wife, Nancy Howe Apfel. She is a child specialist, and in more ways than one. Their son, Darren, is a whizkid of sorts and attends meetings of the Acoustical Society on a sporadic basis.

It is appropriate to end this document with a quote from F.V. Hunt. In a letter of his we find, "...[he has a] breadth of scientific interest and a subtle trait that I can only describe as scientific zing. Apfel has it, and he communicates it."

MARTIN GREENSPAN

LAWRENCE A. CRUM