Frequency-time correlation of surface scattered underwater sound.
frequencytimecor00loom.pdf (5.387Mb)Abstract
The wind driven surface of a large anechoic tank was used
to study forward scattered underwater sound. A 10 kHz saw-tooth
signal was used to drive an omnidirectional source to
insonify the rough surface. Direct and reflected path sound
signals to a point hydrophone were separated by appropriate
gating and the reflected path signal was analyzed for up to
2 minutes at 10 and 20 msec, intervals, using digital FFT
spectral analysis. Graphs of sound pressure level vs. time
for every 10 kHz from 30 kHz to 120 kHz (Surface roughnesses
between 1.1 and 10.5) are shown. Correlation of the scattered
sound pressure with frequency was analyzed. Evidence is presented
to support the hypothesis that, for large roughnesses,
the instantaneous scattered sound amplitudes are harmonic
functions of sound frequency; that is, there is a consistent
frequency separation between instantaneous amplitude maxima
at one frequency and minima at another frequency.
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