Sonar (Magill’s Guide to Military History)
A term derived from “sound navigation ranging,” sonar is a means of determining by acoustic means the direction and distance of objects under water. Sound waves are emitted, reflected off objects in the water, and retrieved and analyzed. A crude sonar system—a series of microphones towed behind a ship—was used to detect submarines during World War I (1914-1918). Subsequent experimentation led to such important devices as the echo sounder, or depth detector, rapid-scanning sonar, WPESS (within-pulse electronic sector-scanning), and rapid scanning sonar. Sonar continues as an important method of detecting submarines, but is also used for other military purposes. Of special note are the use of sonar in directing acoustic homing missiles, detonating acoustic mines, and in detecting other mines.
(The entire section is 122 words.)
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Sonar (Encyclopedia of Science)
Sonar, an acronym for sound navigation and ranging, is a system that uses sound waves to detect and locate objects underwater.
The idea of using sound to determine the depth of a lake or ocean was first proposed in the early nineteenth century. Interest in this technique, called underwater ranging, was renewed in 1912 when the luxury sailing vessel Titanic collided with an iceberg and sank. Two years later, during World War I (19148), a single German submarine sank three British cruisers carrying more than 1,200 men. In response, the British government funded a massive effort to create an underwater detection system.
The entire operation was conducted in complete secrecy, but the first working model was not ready until after the war ended. The project operated under the code name "asdic" (which stood for Allied Submarine Detection Investigating Committee). The device kept that name until the late 1950s, when the American term "sonar" was adopted.
How it works
The principle behind sonar is simple: a pulse of ultrasonic waves is sent into the water where it bounces off a target and comes back to the source (ultrasonic waves are pitched too high for humans to detect). The distance and location can be calculated by measuring the time it takes for the sound to return. By knowing the speed of...
(The entire section is 464 words.)