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Ocean temperature varies with depth, but at between 30 and 100 meters there is often a marked change, called the thermocline, dividing the warmer surface water from the cold, still waters that make up the rest of the ocean. This can frustrate sonar, because a sound originating on one side of the thermocline tends to be bent, or refracted ...
Output of a computer model of underwater acoustic propagation in a simplified ocean environment. A seafloor map produced by multibeam sonar. Underwater acoustics (also known as hydroacoustics) is the study of the propagation of sound in water and the interaction of the mechanical waves that constitute sound with the water, its contents and its boundaries.
A sailor and a man on shore, both sounding the depth with a line. Depth sounding, often simply called sounding, is measuring the depth of a body of water.Data taken from soundings are used in bathymetry to make maps of the floor of a body of water, such as the seabed topography.
There's a lot of tidal movement under the ocean's surface, but we haven't had a great understanding of it so far. Internal tides, created around continental shelf breaks, are far more difficult to ...
Echo sounding is a special purpose application of sonar used to locate the bottom. Since a historical pre-SI unit of water depth was the fathom, an instrument used for determining water depth is sometimes called a fathometer. Most charted ocean depths are based on an average or standard sound speed.
A multibeam echosounder is a device typically used by hydrographic surveyors to determine the depth of water and the nature of the seabed. Most modern systems work by transmitting a broad acoustic fan shaped pulse from a specially designed transducer across the full swathe acrosstrack with a narrow alongtrack then forming multiple receive beams (beamforming) that are much narrower in the ...
Sonar (sound navigation and ranging) is a technique that uses sound propagation under water (or occasionally in air) to navigate, communicate or to detect other vessels. There are two kinds of sonar – active and passive. A single active sonar can localize in range and bearing as well as measuring radial speed.
Sonar systems are generally used underwater for range finding and detection. Active sonar emits an acoustic signal, or pulse of sound, into the water. The sound bounces off the target object and returns an echo to the sonar transducer. Unlike active sonar, passive sonar does not emit its own signal, which is an advantage for military vessels.