Wind effects in shallow-water acoustic transmission.

Acoustic transmission in shallow water is degraded in the presence of high winds; losses can exceed 40 dB, after which they cannot easily be measured. Multifrequency studies have used pulse frequencies f from 312 Hz to 4.44 kHz, with path lengths 17, 23, and 137 km, and observations to about 15 m/s wind speed W. The main results show a dB attenuation proportional to f1.5W4, with a coefficient that depends on the season. They can be explained by a quantitative theory involving the scattering loss from the waves on the rough sea surface. But the possibility of a component of the scattering or absorption coming from shallow layers of entrained bubbles is not ruled out. Briefer descriptions cover effects of directional dependence, comparison of rising and falling winds, squalls, breakup of fish shoals, swell, fluctuations, and observed effects on sonar displays. [ABSTRACT FROM AUTHOR]