ASA 125th Meeting Ottawa 1993 May

2aAO6. Comparison of two numerical models for acoustic transmission loss in shallow-water waveguides.

Steven G. Kargl

Raymond Lim

Coastal Systems Sta., Dahlgren Div., Naval Surface Warfare Ctr., Code 130B, Panama City, FL 32407-7001

Transmission losses for the propagation of an acoustic wave field due to a point source in shallow water to some point along the water--sediment interface are obtained from a fast-field algorithm (SAFARI) and an exact Green's function benchmark [R. Lim, J. Acoust. Soc. Am. 92, 1593--1611 (1992)]. The shallow water environment is modeled as a horizontally stratified medium where the layer of water is bounded above by a semi-infinite layer of air and below by a sediment consisting of a thin transition layer and a semi-infinite subbottom. The sediment layers can be viscous fluids and viscoelastic solids as well as poroelastic materials in the Green's function benchmark. The calculated transmission losses, that are to be discussed, correspond to a water depth of 12 m and a horizontal range that extends to 1 km. A critical comparison of SAFARI against the exact benchmark suggests that extra care be exercised in the application of fast-field algorithms to shallow water problems, even at long ranges.