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: a device used for finding things that are underwater by using sound waves
Full Definition of SONAR
: a method or device for detecting and locating objects especially underwater by means of sound waves sent out to be reflected by the objects; also: a device for detecting the presence of a vessel (as a submarine) by the sound it emits in water
Technique for detecting and determining the distance and direction of underwater objects by tracking acoustic echoes. The name derives from sound navigation ranging. Sound waves emitted by or reflected from an object are detected by sonar apparatus and analyzed for information. In active sonar a sound wave is generated that spreads outward and is reflected back by a target object. Passive systems consist simply of receiving sensors that pick up the noise produced by the target (such as a submarine or torpedo). A third kind of sonar, used in communication systems, requires a projector and receiver at both ends. Sonar was first used to detect submarines in 1916. Modern nonmilitary uses include fish finding, depth sounding, mapping of the ocean floor, Doppler navigation (seeDoppler effect), and searching for wrecks or other objects in the oceans.