Langevin Develops Active Sonar (Great Events: 1900-2001)
Article abstract: Active sonar was developed to detect submarines but is also used in navigation, fish location, and ocean mapping.
Active Sonar, Submarines, and Piezoelectricity
Sonar, which stands for sound navigation and ranging, is the American name for a device that the British call “asdic.” There are two types of sonar. Active sonar, the more widely used of the two types, detects and locates underwater objects when those objects reflect sound pulses sent out by the sonar. Passive sonar merely listens for sounds made by underwater objects. Passive sonar is used mostly when the loud signals produced by active sonar cannot be used (for example, in submarines).
The invention of active sonar was the result of American, British, and French efforts, although it is often credited to Paul Langevin, who built the first working active sonar system by 1917. Langevin’s original reason for developing sonar was to locate icebergs, but the horrors of German submarine warfare in World War I led to the new goal of submarine detection. Both Langevin’s short-range system and long-range modern sonar depend on the phenomenon of “piezoelectricity,” which was discovered by Pierre and Jacques Curie in 1880. (Piezoelectricity is electricity that is produced by certain materials, such as certain crystals, when they are subjected to pressure.) Since its invention, active sonar has been...
(The entire section is 1099 words.)
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