Signal Enhancement of Specularly Scattered Underwater Sound.
NAVAL POSTGRADUATE SCHOOL MONTEREY CALIF
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The aim of this work is to show that the fluctuations of sound caused by surface specular scattering are to some extent predictable. Thus the energy associated with these signals, normally discarded, can be utilized. The wind driven surface of a model ocean was used to study the simultaneous amplitude fluctuations of 31 specularly scattered harmonic components from 5 kHz - 160 kHz. The temporal variations of the scattered components show maxima and minima whose anticorrelation depends on the sound frequency ratio. Significant signal enhancement can be obtained through timely frequency switching between a base frequency and its second harmonic. This gain is found to depend on the effective surface roughness, the duration of the experiment, and the switching threshold.
- Physical and Dynamic Oceanography