Relationship between Deep-Water Ambient Noise and Local Wind Field Fluctuations

Abstract

The results of two comprehensive independent investigations on ambient noise and wind field fluctuations versus wind speed are combined to postulate an interconnection between deep water ambient noise and the short term fluctuations about the local mean wind field. The model considers the air/sea interface to be a time changing acoustic impedance and that energy is extracted from the wind field via a turbulent boundary layer. The combined results indicate that for frequencies above 446 cps, the sound pressure level in dB is linearly related to 20 log of the short-term speed fluctuations, and that for lower frequencies down to 112 cps, the SPL approaches this relationship for mean wind speeds above 22 knots. This model affords a reasonable explanation for the observed fact that at high wind speeds, the level of ambient noise is less sensitive to changes in wind speed. Data that represent a direct evaluation of the postulate that ambient noise is physically linked to the kinetic energy of the local wind-speed fluctuations will be presented.