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Kenneth S. Suslick
School of Chemical Sciences University of Illinois at Urbana-Champaign 600 South Mathews Avenue Urbana, Illinois 61801 USA
Ultrasonics research in the United States began in a secretive private laboratory built in the mansion of the investment banker Alfred Lee Loomis.
Inaudible sound is an oxymoron, so perhaps it is no surprise that the idea of sound with frequencies above human hearing was not well-defined until the early 1800s. Such sound was initially called either “supersonics” or “ultrasonics,” with the latter eventually winning out. Ultrasonics came into the modern era after the collision of the Titanic with an iceberg in 1912 and the coming advent of submarine warfare. The beginning of the twentieth century launched a new and urgent need for under- water sensor technology for the detection of underwater objects. In this historical overview, we look back at the founders of modern ultrasonics through vignettes of a most interesting set of scientists.
Finding the Subs: Paul Langevin and Robert William Boyle
A few weeks after the sinking of the Titanic, Lewis Fry Richardson (inventor of frac- tals) applied for a patent on ultrasonic echo-ranging underwater, but the technology to produce high-intensity ultrasound at the time was simply insufficient. Just three years later, however, a young Russian electrical engineer working in France, Con- stantin Chilowsky, proposed a plan for submarine detection based on Richardson’s echo-ranging concept. The French government asked Paul Langevin (Figure 1, left), then in Paris, for an evaluation of the idea. Langevin was a well-known physicist with expertise in magnetic phenomena and piezoelectricity. Chilowsky and Lan- gevin initiated a project in Langevin’s laboratories, made some progress, and applied for a patent in 1915, but their working relationship was rocky and Chilowsky soon left the project.
The test program was then transferred to the Toulon naval base in southern France. Langevin was responsible for a key invention in the pursuit of high-intensity ultra- sonics. Although his initial single-crystal quartz piezoelectric transducers were encouraging, the voltages required to drive them were too high for practical use. In addition, finding quartz specimens of the size required in quantity was also impractical. Langevin then devised a steel-quartz-steel sandwich transducer, where the resonance was determined by the overall thickness of the whole assembly, not the quartz crystal. In the first tests, single pieces of very large quartz crystals were cemented between the steel plates with a diameter of 20 cm.
There was a synergism to be had among the research expertise of the Allies. The British were pioneers in underwater listening devices (i.e., hydrophones), whereas the French excelled in generating high-intensity ultrasound. In 1916, a joint French- British effort was initiated under the direction of the British Board of Invention and Research (BBIR) and Lord Ernest Rutherford, who had received the Nobel Prize in physics eight years earlier. Research on submarine detection was given a high priority and progressed rapidly, largely due to Langevin and to the development
The Dawn of Ultrasonics and the Palace of Science
 38 | Acoustics Today | Winter 2019 | volume 15, issue 4 ©2019 Acoustical Society of America. All rights reserved.

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