A normal mode model for estimating low-frequency acoustic transmission loss in the deep ocean.

Abstract

This work describes a computer model (QMODE) which uses the normal mode method for the estimation of low-frequency long-range acoustic transmission loss in the deep ocean. Wentzel-Kramer-Brillouin (WKB) solutions for the phase speeds (eigenvalues) and modes (eigenfunctions). The WKB solutions are extended to consider the effects of the surface and bottom boundaries. The eigenvalues are initially estimated by a least-squares polynomial fit through sample results of the WKB characteristic equation. The effects of range dependence in the sound speed profile are simulated through the use of the adiabatic assumption, which has been extended to include the case of profiles with multiple sound channels. Results of the model agree generally with the transmission loss observed in two long-range acoustic experiments.