A computer model for sound propagation around conical seamounts

Abstract

This paper demonstrates a technique for computing the long-range sound pressure field around a penetrable conical seamount. The pressure field is generated by a harmonic point source. The seamount is positioned in a vertically stratified ocean. It is modeled as an outgrowth of the sediment layer covering the ocean bottom. First, the seamount is decomposed into superposed rings of diameters increasing with the depth. Thus the problem reduces to a cylindrically layered system. Then, the method of normal modes is used to compute the sound pressure field in each layer. In order to maintain numerical stability, the Direct Global Matrix approach is used. The radial eigenfunctions are expressed as functions of normalized Hankel and Bessel functions, and the linear system that arise is organized in an unconditionally stable matrix. The results show a perturbation zone behind the seamount. It is bounded by two lines going from the source and tangent to the ring that is at the depth of the source. The values of the sound pressure inside the perturbation zone can be higher or lower than the values outside of it, according to the dimensions of the seamount.