ASA 125th Meeting Ottawa 1993 May

1pAO4. Modeling issues for predicting sound propagation at moderate frequencies in bottom-limited sound channels.

Frederick D. Tappert

Michael G. Brown

Harry A. DeFerrari

Charles Monjo

Lan Nghiem-Phu

Div. of Appl. Marine Phys., RSMAS/U.M., 4600 Rickenbacker Cswy., Miami, FL 33149-1098

Consider sound propagation in the moderate frequency range (depth to wavelength ratio, H/(lambda), between 20 and 100) in shallow water environments with bottom roughness. Measurements in the Straits of Florida have shown remarkable phase stability together with rapid (minutes-to-hours) unstable amplitude fluctuations that nevertheless yield stable envelopes when averaged over many hours. What physical effects should be contained in an acoustic model in order to predict the observed behavior? We suggest that a full-wave model that is capable of multiple rough bottom forward scattering and includes temporally slowly varying range-dependent sound-speed profiles will yield observed results, when used together with coherent signal processing techniques. A broadband PE model will illustrate the assertion, at least qualitatively. Absolute level prediction is quite another matter that requires more extensive environmental inputs.