Existing fiber optic cables can monitor whales

A new study demonstrates for the first time that the same undersea fiber optic cables used for internet and cable television can be repurposed to tune in to marine life at unprecedented scales, potentially transforming critical ...

Seven miles deep, ocean still a noisy place

For what may be the first time, NOAA and partner scientists eavesdropped on the deepest part of the world's ocean and instead of finding a sea of silence, discovered a cacophony of sounds both natural and caused by humans.

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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, the denser fluid. 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.

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