Modeling 3-dimensional sound propagation using the parabolic equation

Abstract

For low frequency sound (below 50 Hz), all ocean propagation is effectively shallow water, as the impact of the seafloor topography impacts the direction and level of acoustic propagation. In this paper, we present a parabolic equation (PE) model, based upon the Range-dependent Acoustic Model (RAM), developed by Michael Collins, which was extended to handle parts of this 3-dimensional acoustic propagation problem. The model, which applies the Pade propagation operator in cross range, after each range step, is well suited to global scale problems where the effects of diffraction and refraction dominate. A quantitative comparison of observations of undersea explosions detonated off the coast of Japan measured from Chile will be presented. In addition to the presentation of this model and it’s application to several observed 3-D propagation effects, a collection of hybrid models used historically to address the out-of-plane propagation will be presented.