ASA 128th Meeting - Austin, Texas - 1994 Nov 28 .. Dec 02

5aUW11. Effect of random volume and surface fluctuations on propagation in shallow water.

Terry E. Ewart

Daniel Rouseff

Appl. Phys. Lab., Univ. of Washington, Seattle, WA 98105

The potential difficulties associated with modeling acoustic propagation in shallow-water environments are well documented. Larger scale deterministic features combine with random fluctuations in the water column, sediment, sea surface, and bottom to produce an extremely complicated propagation regime. The extent to which each of these features needs to be included in realistic propagation models remains to be quantified. Towards this end, results from a series of detailed simulations generated using the parabolic equation (PE) method are presented. Beginning with a deterministic downward refracting sound-speed profile and a known sloping bottom, realizations of the random features are sequentially added to the simulation. Pierson--Moskowitz surface waves, power-law bottom roughness, and representative bottom absorption are used to model the medium. The individual and cumulative effects of these scattering mechanisms on the acoustic wavefront are evaluated. Successive interactions with a random bottom are studied. The results are quantified by using a modal decomposition and also by examining the local arrival angle of energy as a function of depth. [Work supported by ONR.]