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Figure 1. Left: photo of Paul Langevin (1872–1946), taken from a group photo after a luncheon in honor of Albert Einstein convened by Langevin at his home in Paris, 1920. Photo courtesy of the Welcome Collection under the Creative Commons license with attribution. Right: Robert William Boyle (1883–1955). Photo courtesy of the Wikimedia Creative Commons license with attribution.
of practical transducers by Robert William Boyle (a former Rutherford student; Figure 1, right). The British-French joint effort was brilliantly successful in just two years, and early versions of the technology were being installed on Royal Navy warships (HMS Antrim and then HMS Osprey) just after World War I came to an end.
Boyle played the primary role for the British effort on the active sound detection project, producing a prototype for testing at sea by mid-1917. Boyle used composites of quartz mosaics (as shown in Figure 2), alleviating the need for large quartz crystals, and produced the first practical underwater active-sound detection in the world. To maintain secrecy, no mention of ultrasound or quartz was made; the made- up word ASDIC (from Anti-Submarine Division) was used, which eventually became known as “sonar” (for “sound navi- gation and ranging” in analogy with “radar”).
Beyond his direct work on sonar, Boyle was the first to observe acoustic cavitation from the ultrasonic irradiation of liquids, a point rather important to the chemical and physical effects of ultrasound and likewise to the underwa- ter propagation of high-intensity ultrasound. Boyle (1928) is also notable for having written the first major review on ultrasonics, which, unfortunately, was published in a journal that went bankrupt soon after. Thus, Boyle’s review had rather limited impact.
By way of background, Langevin completed college at the École Normale Supérieure, went to Cambridge to study with J. J. Thomson, and returned to the Sorbonne, obtaining his PhD in 1902 under the supervision of Pierre Curie, codiscov- erer of piezoelectricity, future Nobel Laureate, and husband of Marie Curie. In 1904, Langevin was appointed to the Col- lège de France (Paris), where among his doctoral students were future Nobelists Irene Joliot-Curie (daughter of Pierre and Marie) and Louis de Broglie. After World War I, Lan- gevin, along with some French entrepreneurs, succeeded in commercializing marine ultrasonics and produced a depth- sounding instrument that was installed on many ships during the 1920s. In 1940, capping his many successes, Langevin received the Copley Medal of the Royal Society (the oldest surviving scientific award in the world). Langevin was politi-
Figure 2. a and b: Cross-sectional views of two forms of quartz transducers designed by Boyle, recorded in British Board of Invention and Research (BBIR) document 38164/17. c: Both transducers have a mosaic of quartz elements as shown, thereby obviating the need to use large single crystals. These transducers (50 cm2 at 75 kHz) in October 1917 transmitted signals nearly a mile in open ocean.
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