Application of ray tracing with horizontal gradient to monostatic boundary reverberation

Abstract

Presented is the current work being done at the Naval Research Laboratory (NRL) on the development of a series of computer programs to predict long range, low frequency, monostatic boundary reverberation. The emphasis is on the ray tracing technique and its application to the special problems of estimating the transmission loss of rays that hit the boundaries of the medium. The ray tracing technique is to increment a ray from point to point along its ray path by evaluating Taylor series expansions in arc length of various ray parameters such as range, depth, travel time, and range angle, which are based on the ray equation. Possible horizontal variations in sound speed are accounted for by allowing multiple input profiles. Also, a linearly segmented ocean bottom and a flat surface are assumed. Monostatic boundary reverber.ation 1S estimated by means of a range dependent formulation developed at NRL. An underlying assumption of this formulation is that when a ray encounters a boundary, it continues to propagate in the direction of specular reflection, while a small amount of the incident radiation is scattered in all directions. By reciprocity, scattered energy will return to the source-receiver back along those ray paths emitting from the source and passing through the boundary point at which the hit occurred.