ASA 124th Meeting New Orleans 1992 October

1pUW8. The influence of a bubbly layer on near-surface acoustic propagation and surface loss modeling.

Raymond J. Christian

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

The impact of refraction, attenuation, and scattering due to a near-surface bubbly layer on acoustic propagation modeling can be significant in appropriately sensitive surface duct and shallow water environments. Hall [J. Acoust. Soc. Am. 86, 1103--1117 (1989)] presents a semi-empirical acoustic model to determine the propagation affects of the bubbly layer on one-way horizontal transmission in a surface duct. Expressions for the depth-dependent complex sound speed and attenuation are used to extend the Hall model to the general near-surface acoustic interaction problem. The rough surface scattering at the air--sea interface and the propagation through the subsurface bubbly layer are treated independently in a simplified approach toward examining the impact of bubbles on modeled surface duct and shallow water transmission loss. The dependence of the ``effective'' surface loss on grazing angle and wind speed are analyzed in the frequency band of approximately 0.5--5 kHz.