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The SOFAR channel (short for sound fixing and ranging channel), or deep sound channel (DSC), [1] is a horizontal layer of water in the ocean at which depth the speed of sound is at its minimum. The SOFAR channel acts as a waveguide for sound, and low frequency sound waves within the channel may travel thousands of miles before dissipating.
The presence of this minimum creates a special channel known as deep sound channel, or SOFAR (sound fixing and ranging) channel, permitting guided propagation of underwater sound for thousands of kilometers without interaction with the sea surface or the seabed. Another phenomenon in the deep sea is the formation of sound focusing areas, known ...
Upsweep is an unidentified sound detected on the American NOAA's equatorial autonomous hydrophone arrays. This sound was present when the Pacific Marine Environmental Laboratory began recording its sound surveillance system, SOSUS, in August 1991. It consists of a long train of narrow-band upsweeping sounds of several seconds in duration each.
Underwater communication is difficult due to factors such as multi-path propagation, time variations of the channel, small available bandwidth and strong signal attenuation, especially over long ranges. Compared to terrestrial communication, underwater communication has low data rates because it uses acoustic waves instead of electromagnetic waves.
The original system was capable of oceanic surveillance with the long ranges made possible by exploiting the deep sound channel, or SOFAR channel. An indication of ranges is the first detection, recognition and reporting of a Soviet nuclear submarine coming into the Atlantic through the Greenland-Iceland-United Kingdom (GIUK) gap by an array ...
The sound's source was roughly triangulated to , a remote point in the South Pacific Ocean west of the southern tip of South AmericaThe sound was detected by the Equatorial Pacific Ocean autonomous hydrophone array, [1] a system of hydrophones primarily used to monitor undersea seismicity, ice noise, and marine mammal population and migration.
Sounds emitted at or near the axis of this channel propagate for very long horizontal distances, owing to the refraction of the sound back to the channel's center. [ 2 ] Sound speed profile data are necessary for underwater acoustic propagation models, especially those based on ray tracing theory.
A spectrogram of Upsweep. Upsweep is a sound detected by the U.S. National Oceanic and Atmospheric Administration's (NOAA) equatorial autonomous hydrophone arrays. The sound was recorded in August, 1991, using the Pacific Marine Environmental Laboratory's underwater sound surveillance system, SOSUS, and is loud enough to be detected throughout the entire Pacific Ocean.