Hydrophone

Ranked #3 on the list Best Measuring Instrument of All Time

7.17
Based on 6 votes

About Hydrophone

  • Dimension measured:
  • Subclasses: Ocean Bottom Hydrophone
  • Subclass of:

A hydrophone (Greek "hydro" = "water" and "phone" = "sound") is a microphone designed to be used underwater for recording or listening to underwater sound. Most hydrophones are based on a piezoelectric transducer that generates electricity when subjected to a pressure change. Such piezoelectric materials, or transducers can convert a sound signal into an electrical signal since sound is a pressure wave. Some transducers can also serve as a projector, but not all have this capability, and may be destroyed if used in such a manner. A hydrophone can "listen" to sound in air, but will be less sensitive due to its design as having a good acoustic impedance match to water, which is a denser fluid than air. Likewise, a microphone can be buried in the ground, or immersed in water if it is put in a waterproof container, but will give similarly poor performance due to the similarly bad acoustic impedance match. The earliest widely used design was the Fessenden oscillator, an electrodynamically driven clamped-edge circular plate transducer (not actually an oscillator) operating at 500, 1000, and later 3000 Hz. It was originally marketed as an underwater telegraph, rather than as sonar, but

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