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May 1, 2014 · In Britain, active detection became known as ASDICS. In 1942, F.V. Hunt, the director of Harvard’s wartime Underwater Sound Laboratory created the word “sonar.” By 1943, the U.S. Navy adopted the word “sonar” (Sound Navigation And Ranging) as the generic term for the use of acoustic waves in active detection.
Mar 1, 2024 · As the sound waves bounce off these particles and scatter back to the sensor, the ADCP measures the frequency shift caused by the motion of the particles relative to the emitted frequency. This shift allows the ADCP to determine the speed and direction of water movement at various depths, providing a profile of current velocities from the surface to the bottom.
To support the HF transmitters, NRL developed a tuned radio frequency HF receiver in the mid 1920s. A commercial procurement made the receiver available to various ships, shore stations, the Marine Corps, and the U.S. Coast Guard. A later receiver was produced in quantity, (about 1000) and provided throughout the naval service.
Mar 6, 2017 · Other marine mammals including the pinnipeds (seals and sea lions) make and listen to sounds for a variety of important communicative and orientation functions, but like the large whales they appear to lack specialized high-frequency echolocation (biosonar) systems (Schusterman, 1981; Wartzok and Ketten, 1999; Schusterman et al., 2000). Sounds produced by these species are largely in social ...
- Brandon L. Southall, Amy R. Scholik-Schlomer, Leila Hatch, Trisha Bergmann, Michael Jasny, Kathy Met...
- 2017
More importantly, high-frequency ultrasound waves generally provide a better spatial resolution compared to low-frequency ultrasound waves, though with a limited penetration depth [280]. In marine composites, for example, successful examinations are typically performed at the lower end of the ultrasound frequency band (0.5–2.25 MHz) [12,281].
The sound waves emitted by an echo sounder are typically in the range of 20 to 200 kHz, which is beyond the range of human hearing. The higher the frequency of the sound wave, the more accurate the depth measurement will be, as high-frequency sound waves can detect smaller objects and features on the ocean floor.
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May 1, 2022 · The validity of this approximation depends on detailed knowledge of various factors, including the distance to the sound source, proximity of sea surface and seabed boundaries that could impact wave propagation, size of the sound source, cut-off frequency, wavelength of the sound, and variation in sound propagation (Nedelec et al., 2016). Such information is rarely available in the shelf seas ...
