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of Merit for his service to the NSRL and went on to become president of the University of Pennsylvania. Carl Eckart was NSRL’s preeminent theoretical physicist and went on to win the ASA Pioneers of Underwater Acoustics Medal in 1973 (all shown in Figure 9).
The UCDWR’s San Diego laboratory carried out research and experiments on a long list of oceanographic and ocean acoustic effects, including currents, water temperature, salinity, bathymetry, and other ocean variables as well as sound propagation, scattering, target strengths, reverbera- tion, and ambient noise. The basic knowledge needed to improve sonar and the use of Navy systems was developed as were adjunct sonar devices. The UCDWR also ran an ex- tensive training program for naval personnel and staff sci- entists deployed with the fleet to support equipment testing and use, and to advise on acoustics issues (Kuperman, 2015; Rees, 2015).
ing in summer research cruises aboard WHOI’s R/V Atlantis with his students, including J. Lamar (Joe) Worzel, who was to be associated with Ewing for a professional lifetime (Fig- ure 10). In 1940, Ewing and his students came to WHOI for the duration of the war, bringing underwater acoustics to the institution. They included Alan Vine, Brackett Hersey, and Frank Press, who went on to become president of the National Academy of Sciences (Lynch et al., 2015).
Figure 10. Maurice Ewing, J. Lamar Worzell, and Chaim L. Pekeris (left to right).
Underwater acoustic experiments were done with explosive shot sources, hydrophones in the water column, and geo- phones on the shallow seafloor. Acoustic experiments were enhanced by the measurement of ocean parameters such as bathythermograph logging of the ocean temperature-depth profile. Worzell and Ewing (1948) made shallow-water measurements along the East Coast and studied sediment and water column propagation to discover and describe dispersive features of broadband acoustic pulses. The data sets were analyzed by Chaim Pekeris (1948; Figure 10) of the Columbia University Mathematical Physics Group. He carefully studied the measurement results and developed the first theoretical shallow-water, normal-mode model, which bears his name and continues to this day as a benchmark.
Ewing is credited with first predicting and then making the first measurements on the sound fixing and ranging (“SO- FAR”) sound channel, created by decreasing temperature and increasing pressure with depth in the deep ocean, thus creating a minimum in the sound speed-depth profile (Ew- ing and Worzel, 1948). This effect enables long-range propa- gation within a deep horizontal zone. Leonid Brekhovshikh independently found this result through the study of ex- perimental data in the Soviet Union (Brekhovskikh, 1949; Godin and Palmer, 2008; Godin, 2015). The SOFAR channel enabled downed pilots to signal for help with a small explo- sive charge.
Figure 9. Vernon Knudsen, Gaylord Harnwell, and Carl Eckart (left to right).
Experts were widely recruited from unique backgrounds for tasks such as precision sound recording. Among these was Arthur Roshon, who came from Walt Disney Studios in Hollywood, to lead a major accomplishment on the de- velopment of a high-frequency continuous transmission frequency-modulated (CTFM) sonar system, designated the QLA, which was installed on 45 US submarines and proved extremely useful in mine avoidance in operations in heavily mined inland seas (NDRC, 1946d). Another major project was the development of decoys designed to simulate subma- rines, and over 4,000 of these saw service in the fleet (NDRC, 1946e).
WHOI was founded in 1930 at the instigation of the Na- tional Academy of Sciences and a grant from the Rockefeller Foundation and was guided by visionaries such as Henry Bigelow and Frank Lille. Beginning in 1935, geophysics pro- fessor Maurice Ewing of Lehigh University began participat-
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