Measurement of source-receiver motion with underwater sound

Article By:

Frisk, George V. Applied Ocean Physics and Engineering Department, Woods Hole Oceanographic Institute, Woods Hole, Massachusetts.

Last reviewed:2002

DOI:https://doi.org/10.1036/1097-8542.YB020965

Sound is the most powerful remote sensing tool available for use in the sea. In contrast to electromagnetic waves, which are attenuated over very short distances underwater, sound waves at low frequencies (less than 500 Hz) can propagate over extraordinarily long ranges (thousands of miles) without significant distortion or loss of energy. The use of underwater sound as a technique for detecting submarines began during World War I and accelerated rapidly during World War II. During the Cold War, acoustic antisubmarine warfare became the principal deterrent against missile-carrying submarines roaming the high seas. It was during the latter period that ocean acoustics transcended these militarily motivated applications and emerged as a fundamental scientific discipline encompassing a broad range of topics in wave propagation physics, electrical engineering, oceanography, and geophysics. These rapidly developing scientific advances spawned the new discipline of acoustical oceanography, in which sound is used as a probe to measure oceanographic properties of the water column, the seabed, and the sea surface. Since the end of the Cold War, ocean acoustics has retained its military significance, now in the context of third-world nations potentially posing submarine threats in shallow-water areas. It is in this shallow-water context that new and exciting results have emerged in the area of tracking sound sources by measuring the phase of the low-frequency tones that they emit. These developments have general implications for the deep-water scenario as well.

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