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Biomass estimation is a method of detecting and quantifying fish and other marine organisms using sonar technology. [1] An acoustic transducer emits a brief, focused pulse of sound into the water. If the sound encounters objects that are of different density than the surrounding medium, such as fish, they reflect some sound back toward the source.
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.
Underwater acoustic communication is a technique of sending and receiving messages in water. [1] There are several ways of employing such communication but the most common is by using hydrophones . Underwater communication is difficult due to factors such as multi-path propagation , time variations of the channel, small available bandwidth and ...
The exact extent of what can be discerned depends on the frequency and power of the pulse transmitted. Knowing the speed of the wave in the water, the distance to the object that reflected the wave can be determined. The speed of sound through the water column depends on the temperature, salinity and pressure (depth).
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.
A long-range acoustic device (LRAD), acoustic hailing device (AHD) or sound cannon is a specialized loudspeaker that produces sound at high power for communicating at a distance. It has been used as a method of crowd control , which has caused permanent hearing damage , having an extremely high decibel capacity (up to 160 dB measured at one ...
A 4-inch (100 mm) underwater locator beacon, with ballpoint pen for scale A ULB attached to a bracket on a cockpit voice recorder. An underwater locator beacon (ULB), underwater locating device (ULD), or underwater acoustic beacon is a device that emits an acoustic pulse intended to guide searchers equipped with a suitable receiver to the location of the beacon underwater.
In nautical terms, the word sound is used to describe the process of determining the depth of water in a tank or under a ship. Tanks are sounded to determine if they are full (for cargo tanks) or empty (to determine if a ship has been holed) and for other reasons.