ASA 124th Meeting New Orleans 1992 October

1aUW2. Sensitivity of shallow water transmission loss to source and receiver proximity to a hard bottom under downward refracting conditions.

Peter D. Herstein

Bernard F. Cole

David G. Browning

Frank L. Groneman

Naval Undersea Warfare Ctr., New London Detachment, New London, CT 06320

Under downward refracting conditions, raypaths from a shallow source will tend to have grazing angles at a hard bottom that are greater than the critical angle and therefore suffer a relatively large loss per bounce. As the source depth increases, lower grazing angles can be obtained. When the grazing angle becomes less than the critical angle, bottom loss per bounce is significantly reduced allowing a possible reduction in propagation loss. An analysis is made for a North Atlantic shallow water area south of Long Island under summer conditions to determine the sensitivity of transmission loss to changes in source and receiver depth for ranges up to 50 km. The results are compared to the previous results of Cole and Podeszwa [B. F. Cole and E. M. Podeszwa, J. Acoust. Soc. Am. 41, 1479--1484 (1967)].