Underwater acoustic communication channel characterization in the presence of bubbles and rough sea surfaces

Abstract

In this paper we model the underwater acoustic communication channel in shallow water. We put particular emphasis on the effect of the bubbles caused by wave breaks under strong winds. Underwater bubble clouds provide locally significant modifications of the sound speed field. The modified sound speed field contributes to a major transmission loss to sound propagation and scattering of the signals. We adopt the bubble field model developed by Norton, et al., generate range dependent discrete bubble plumes and compute the sound speed profile of each bubble plume. In addition, we model the rough surface using a spectral model to generate realizations of rough sea surfaces. With a bubble perturbed sound speed field and sea surface spectrum, we model the communication channel using a rough surface parabolic equation model to generate a complex pressure field at a selected set of ranges and depths. These pressure fields form the basic frequency response of the channel. Our results show that under strong winds, bubbles contribute to large transmission loss and cannot be neglected. Furthermore, for high wind speeds the dominate attenuation mechanism is the scattering from the bubble plumes rather than the scattering from a rough sea surface.