Brian H. Tracey
Henrik Schmidt
Dept. of Ocean Eng., MIT, 77 Massachusetts Ave., Bldg. 5-007, Cambridge, MA 02139
Rough surface scattering in ocean waveguides causes a loss of signal coherence and transfers energy between the guided modes of the waveguide. These effects are important for prediction and signal processing applications, and have been studied using techniques such as coupled mode theory. As an alternate approach, a self-consistent perturbational scattering theory developed by Kuperman and Schmidt [W. A. Kuperman and H. Schmidt, J. Acoust. Soc. Am. 57, 1511--1522 (1989)] is rewritten in terms of a normal mode representation of the pressure field. This approach is significantly less computationally intensive than the wave-number integration formulation used previously. The decay of the coherent field and statistics of the scattered field such as the cross-modal coherences can be calculated. The approach allows an arbitrary number of layers separated by rough interfaces and can be extended to elastic media as well. Numerical results are presented for a realistic shallow-water ocean environment. [Work supported by ONR.]