Three-dimensional Gaussian beam tracing for shallow-water applications

Abstract

Gaussian beam tracing is a ray-based method of acoustic wave propagation that overcomes some of the implementation problems of conventional ray methods, while retaining a speed advantage over wave theory approaches. A fan of Gaussian beams are propagated from a source, according to the standard ray equations, so that the pressure at any given point can be approximated by the sum of contributions from each beam. Eigenray computations, perfect shadows, and infinite caustics associated with standard ray methods are thereby eliminated, and the applicability to lower-frequency problems is improved. Gaussian beam tracing is particularly well suited for three-dimensional problems, for which eigenray computations are costly. The effectiveness of a three-dimensional Gaussian beam model [Bucker, J. Acoust. Soc. Am. 95, 2437–2440 (1994)] for predicting acoustic propagation in shallow water is demonstrated. At low frequencies, Gaussian beam and wave solutions are compared for the ASA benchmark wedge problem and the Shallow Water Acoustic Modeling 1999 Workshop Gaussian canyon problem. The use of the model for the analysis of three-dimensional bathymetric effects in real data will also be demonstrated. At high frequency, model predictions of impulse responses will be compared to measured data for a number of acoustic communications experiments. [Work supported by ONR.]