Stochastic scattering model predictions for reverberation from the near-surface oceanic bubble layer

Abstract

A stochastic bubble-layer scattering model has recently been developed that uses as input the horizontal wave-number spectrum of the sound-speed fluctuations in the bubble layer [K. E. Gilbert and L. Wang, J. Acoust. Soc. Am. 90, 2300 (A) (1991)]. The wave-number spectrum is of the form P(K)=AK−β, where β≊4 is a nearly universal constant that has been inferred from 11 different deep-ocean reverberation experiments. To determine the constant A, one needs to know the rms sound-speed fluctuation in the bubble layer and the horizontal scale of the largest inhomogeneities in the layer (‘‘outer scale’’). In the past year, oceanographic experiments have directly measured these parameters so that predictions with the stochastic scattering model can now be more reliably made. In this paper, the scattering model is briefly reviewed and predictions for backscatter from the bubble layer using measured oceanographic parameters as input are presented. It is shown that with oceanographically constrained parameters (i.e., no ‘‘adjustable’’ parameters) the stochastic scattering model gives a good account of the observed backscatter, as a function of both frequency and angle. [Work supported by ONR.]