hydrophone (hĪˈdrəfōnˌ) [key], device that receives underwater sound waves and converts them to electrical energy; the voltage generated can then be read on a meter or played through a loudspeaker. The hydrophone is the marine equivalent of the microphone, which receives and converts sound waves in air. It is used in sonar apparatus and in certain underwater weapons. The same device may also be used to generate sounds, converting electrical energy to motional mechanical energy; in this capacity it is called a projector.
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