ASA 129th Meeting - Washington, DC - 1995 May 30 .. Jun 06

2pUW25. Comparison of exact and approximate solutions of multiple scattering between interfaces in rough waveguides.

Kevin D. LePage

Bolt Beranek and Newman, Inc., 70 Fawcett St., Cambridge, MA 02138

Modeling propagation in rough waveguides introduces the interesting question of how to treat multiply scattered waves. One approach is to treat the rough surface scattering at the waveguide boundaries under an extended Born approximation [W. Kuperman and H. Schmidt, J. Acoust. Soc. Am. 86 (1989)]. Under this approach multiple scatter effects are incorporated into the mean field through a second-order correction in surface roughness, and the scattering amplitudes at each interface are assumed to be driven by the corrected mean field alone. Coupled integral equations which the total field in a rough waveguide must satisfy at the source depth are available in the literature [D. Berman, J. Acoust. Soc. Am. 92 (1992)], making it possible to evaluate the approximate results in a consistent way. Here the results obtained by solving the integral equations are compared to those obtained by adding the scattered field to either a corrected or an uncorrected mean field. Conclusions regarding the bounding behavior of the approximate solutions are drawn for various roughness and waveguide parameters in the low frequency regime.