Acoustic plane wave incident upon a #uid slab bounded by rough surfaces, within which the sound-speed distribution is subject to random perturbation, is considered. A theory based upon a boundary perturbation method in conjunction with a formulation derived from Green's function for the coherent "eld in the random medium has been applied to a typical oceanic environment, to study the coherent re#ection from and transmission through the rough-and-random slab. Under the assumption of independence between the randomness of rough surface and that of sound-speed perturbation, the coherent "elds may be obtained straightforwardly using formulations compatible with those employed in the existing literature. The re#ection and transmission coe$cients are then numerically generated for various cases to analyze the e!ects of surface roughness and medium inhomogeneities. The results have shown that both mechanisms reduce the coherent re#ection and transmission coe$cients, because of the generation of incoherent scattered "elds which in e!ect are to disperse coherent energy. It is also interesting to note that the variation of the re#ection coe$cient near the critical angle presents distinctive characteristics for di!erent scattering mechanisms, potentially allowing to identify the dominant one for a particular problem under consideration.
2001 Academic Press