A THEORETICAL-STUDY OF LOW-FREQUENCY OCEANIC AMBIENT NOISE

This paper describes a theoretical model that predicts the wind-depend ent ambient noise level in the ocean. Wave breaking and subsequent for mation of whitecaps are assumed to be the sole source of sound at the sea surface and their contributions are computed by the use of a simpl e model for the bubble cloud generated by this process. Inverted hemis pherical shapes for which an analytical solution to the wave equation is given are employed to describe the cloud geometry. The input physic al parameters to the model are the bubble-size distribution, the dipol e strength of the entrained bubbles, the cloud size distribution and g rowth rate, and the void fraction of the bubble cloud. By using an emp irical relation between the whitecap coverage ratio and the wind speed , the underwater ambient noise and surface source levels are computed as a function of frequency and wind speed. Calculated noise levels are in good agreement with the field measurements.