A simple 3-D Gaussian beam sound propagation model for shallow water

A simple 3-D Gaussian beam propagation model has been developed for the calculation of acoustic fields in shallow water where variation of bottom depth in range and bearing has a significant effect. The algorithm traces beams in appropriate directions and determines when there is a close approach of a beam to a receiver. When this happens, there is a coherent contribution to the sound field at the receiver that depends upon the history of the beam and the closeness of approach. Examples are given showing reasonable agreement with exact solutions for a negative gradient shallow water channel and two difficult wedge cases.