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Acoustics, the science of sound, starts as far back as Pythagoras in the 6th century BC, who wrote on the mathematical properties of stringed instruments. Echolocation in bats was discovered by Lazzaro Spallanzani in 1794, when he demonstrated that bats hunted and navigated by inaudible sound, not vision. Francis Galton in 1893 invented the Galton whistle, an adjustable whistle that produced ultrasound, which he used to measure the hearing range of humans and other animals, demonstrating that many animals could hear sounds above the hearing range of humans.
The first article on the history of ultrasound was written in 1948.[3] According to its author, during the First World War, a Russian engineer named Chilowski submitted an idea for submarine detection to the French Government. The latter invited Paul Langevin, then Director of the School of Physics and Chemistry in Paris, to evaluate it. Chilowski's proposal was to excite a cylindrical, mica condenser by a high-frequency Poulsen arc at approximately 100 kHz and thus to generate an ultrasound beam for detecting submerged objects. The idea of locating underwater obstacles had been suggested prior by L. F. Richardson, following the Titanic disaster. Richardson had proposed to position a high-frequency hydraulic whistle at the focus of a mirror and use the beam for locating submerged navigational hazards. A prototype was built by Sir Charles Parsons, the inventor of the vapour turbine, but the device was found not to be suitable for this purpose. Langevin's device made use of the piezoelectric effect, which he had been acquainted with whilst a student at the laboratory of Jacques and Pierre Curie.[4] Langevin calculated and built an ultrasound transducer comprising a thin sheet of quartz sandwiched between two steel plates. Langevin was the first to report cavitation-related bioeffects from ultrasound.[5]
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