Acoustical Society of America
Gold Medal Award - 1983

Martin Greenspan

MARTIN (MOE) GREENSPAN was born in New York City on 8 May 1912. After public school in Jersey City he attended the Cooper Union Institute of Technology and received the B.S. degree in 1934. He married Lillian Gunsberg in 1937. They have 2 daughters and a son (Miriam, Ruth, and Robert). He joined the staff of the National Bureau of Standards in the autumn of 1935 and maintained this affiliation to the present day; since retirement in 1974 he has been serving as a consultant.

Until 1946 his work at the Bureau was in the field of elasticity and strength of materials. He performed important theoretical work on the stress distribution in civil engineering structures such as rigid knee bents, box girders, and perforated plates. In such structures the stress distribution can be very complex. Accordingly, closely coordinated theoretical and experimental efforts are necessary if structural safety is to be assured with confidence. He was a member of a team led by the late Dr. A. H. Stang. The results of their efforts are landmarks in the evolution of modern civil engineering practice. Also, Moe's work on stress distribution in perforated plates was an important contribution to modern elastic fracture mechanics. His work was so highly regarded that in 1949 he was awarded the Meritorious Service Award (Silver Medal) of the United States Department of Commerce.

In August 1946, at the invitation of its Chief, Richard K. Cook, Moe joined the Sound Section where he has since done work in Physical Acoustics. In 1966 he became Chief of the Section. His work (with the assistance of Richard K. Cook and Moody C. Thompson, Jr.) on the propagation of sound in rarefied gases, which he started on joining the Section, is by now a classic. He was able to show that the Navier–Stokes equation gave a surprisingly good quantitative account of the attenuation and dispersion of sound in monatomic gases down to a wavelength over mean free path ratio approaching unity. Moreover, he succeeded in making measurements to much lower pressures where the mean free path was significantly greater than the wavelength and found substantial deviations. New theoretical many-body results are now judged by their agreement with these data. For polyatomic gases, where molecular relaxation processes associated with vibrational and rotational modes occur in addition to the translational relaxation, he was able to demonstrate experimentally and theoretically how they combine to affect acoustic dispersion and attenuation. This work was completed about 25 year ago and its importance grows, rather than diminishes, with the years.

In the early fifties the U. S. Navy identified its need for an automatic device to measure the speed of sound in the sea, particularly as a function of depth. Moe and Carl E. Tschiegg collaborated in the development of an accurate, reliable, and rugged instrument now called an acoustic velocimeter, which was the prototype for those used by the Navy on a worldwide basis. Over the years it has found industrial application and today there are many thousands in such use, so that now there are more used in industry than in the ocean. The excellence of this work was recognized and the National Bureau of Standards awarded him and Tschiegg the Meritorious Service Award (Silver Medal). Moe may be the only one at the Bureau who has received more than one Silver Medal.

In the sixties Moe, with Carl E. Tschiegg, turned his attention to cavitation. They paid special attention to the effects of dissolved gases and of neutron irradiation on the threshold of cavitation. The bubbles which form from the dissolved gas and the recoil atomic nuclei from the neutrons form the nuclei for cavitation and consequently lower the threshold. Thresholds determined with neutrons as the nucleating agent are essentially reproducible. Thus in degassed, neutron-irradiated liquids, the temperature dependence of the threshold of cavitation can be reliably determined, which they succeeded in doing for many liquids. This has just been published in The Journal of the Acoustical Society of America, October 1982, Technical Notes and Research Briefs. Moe now has won worldwide recognition as being preeminent in this field..

In acoustic emission measurements it is hoped that the waveform of the signal received characterizes the event which produces the signal. But in such measurements, at least before Moe turned his attention to the problem, the signals were drastically affected by the "ringing" of the specimen and the associated apparatus, with the result that the signal for the most part merely reflected the normal modes of the specimen and apparatus. Moe, along with Franklin R. Breckenridge and Carl E. Tschiegg, was able to develop a technique in which, at least for certain acoustic emission events, the received signals were completely free of aberration due to reflections or ringing. Moreover the apparatus could be adapted to the calibration of transducers.

Moe's latest published foray into theoretical acoustics is in the theory of the piston radiator. One might think that this is a pretty well-worked-over problem. But in a 1979 paper he succeeded in extending the theory to include exact solutions for cases in which the acoustic pressure and particle velocity vary over the face of the piston. This is major contribution to the theory.

The B. S. degree received from the Cooper Union Institute of Technology is Moe's highest academic degree, and ended his formal education. Through his experiments, his writing (he has an expressive style characterized by brevity and incisiveness), and lecturing he has earned an envious international reputation. The great breadth and depth of his knowledge of acoustics is matched by few others in the world today. Theodore A. Litovitz of Catholic University and an expert in ultrasonics wrote, "I have been most affected, not to mention directed and corrected, by his encyclopedic understanding of acoustical phenomena. For over 25 years I have regarded Moe as the `Guru' of physical acoustics."

During the academic year 1958–1959 he was a visiting lecturer at the UCLA physics department. At the end of his stay he turned down their offer of a high-level Full Professorship to return to NBS to which he is devoted. He has also taught courses in mathematics, engineering, and physics at the University of Maryland, Catholic University, George Washington University, NBS Graduate School, and the U. S. Department of Agriculture Graduate School.

It is a delight to observe him at meetings of our Society. His presentations at technical sessions have style, good humor, are colorful and clear, and all have solid scientific content. On the other side of the coin, the technical sessions benefit greatly from his presence in the audience. With Moe's encyclopedic knowledge he finds ample opportunity to raise questions and make comments. I've been in innumerable sessions where such responses were more important than the paper itself and often increased its significance. He is a master of corridorship. Where you find Moe you'll usually find a circle of young and old listening to him tell the way it was and the way it is, or just telling a good story in his inimitable way.

Moe has long been a Fellow of the Acoustical Society of America. He was elected to the Executive Council in 1959–1962. He was elected Vice President in 1963–1964, President-Elect in 1965-1966, and served as President in 1966–1967. In 1967–1968 he was Chairman of the Technical Council of the Society. He was a member of the Technical Committee on Physical Acoustics in 1961–1964, and in 1968–1971. He has served as the Acoustical Society's representative on the Council of the AAAS, on the U. S. National Committee of the International Union of Pure and Applied Physics, and on the Division of Physical Sciences of the National Research Council. In the Washington, DC Chapter of the Society, he was Vice-Chairman in 1960 and Chairman in 1961. He served as an Associate Editor of our Journal during 1961–1966, and Editor of the Journal of Research of the National Bureau of Standards Section C 1962–1973. He was our Society's representative on the Governing Board of the American Institute of Physics 1974–1979.

In addition to the two Meritorious Service Awards of NBS already mentioned he has received the Acoustical Society Silver Medal in Physical Acoustics (1977) and the Harry Diamond Award given by the IEEE (1980).

He is a Fellow of the American Physical Society, of the Washington Academy of Sciences, of the American Association for the Advancement of Science, and is a member of the Philosophical Society of Washington.

This encomium can hardly be ended better than with the words of one of our younger and brightest members who wrote a supporting letter for the nomination of Moe for the Gold Medal. He started his letter with "Martin Greenspan" is the kind of scientist I would like to be." He ended it with "For the enrichment to the scientific literature, and, equally important, for the enrichment of our lives, Martin Greenspan is pure gold all the way."

Isadore Rudnick