Three-dimensional underwater sound pressure sensitivity in oceanic environments

Abstract

Physical oceanographic processes, marine geological features, sub-bottom geoacoustic structure, sea surface disturbances, etc., can either individually or jointly affect underwater sound propagation in the ocean and cause significant temporal and spatial variability in the sound pressure field. The primary goal of this study is to develop a numerical scheme to determine the sound pressure sensitivity in response to variations of index of refraction due to changes of environmental conditions. This sensitivity analysis is an exention of the Born approximation which assumes perturbations at infinitesimal points. To handle disturbance within a finite volume, an improved sensitivity kernel is derived from a higher-order parabolic-equation (PE) approximation. With this sensitivity kernel, we can analyze the spatial distribution and the temporal evolution of the acoustic sensitivity field in complex oceanic environments. This paper will present numerical examples of three-dimensional (3D) sound propagation in continental slopes, submarine canyons, and nonlinear internal wave fields. Discussions on other applications, including uncertainty quantification of transmission loss prediction and adjoint models for 3D acoustic inversions, will also be provided. [Work supported by the Office of Naval Research.]