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The main cause of sound attenuation in fresh water, and at high frequency in sea water (above 100 kHz) is viscosity. Important additional contributions at lower frequency in seawater are associated with the ionic relaxation of boric acid (up to c. 10 kHz) [ 7 ] and magnesium sulfate (c. 10 kHz-100 kHz).
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.
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 ...
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.
The speed of sound will vary slightly depending on temperature, pressure and salinity; and for precise applications of echosounding, such as hydrography, the speed of sound must also be measured, typically by deploying a sound velocity probe in the water. Echo sounding is a special purpose application of sonar used to locate the bottom.
As sound travels faster and over a larger distance in water than in air, aquatic animals can use sound signals for long-distance communication while terrestrial animals cannot. [4] For example, a blue whale can communicate with another blue whale using sound over thousands of miles across the sea.
Raj Matharu, 31, of Northridge, faces one count of possession with intent to distribute methamphetamine, according to the U.S. Attorney's Office.
An additional benefit of the coating was it acted as a sound dampener, containing the U-boat's own engine noises. [1] Alberich tiles as they appear on U-480. The coating had its first sea trials in 1940, on U-11, a Type IIB. [1] [5] U-67, a Type IX, was the first operational U-boat with this coating. [2]