ACOUSTIC PLANE WAVE INTERACTION WITH A RANDOMLY INHOMOGENEOUS SLAB BOUNDED BY ROUGH SURFACES

Acoustic plane wave incident upon a fluid 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 Greenʹs function for the coherent field in the random medium has been applied to a typical oceanic environment, to study the coherent reflection 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 fields may be obtained straightforwardly using formulations compatible with those employed in the existing literature. The reflection and transmission coefficients are then numerically generated for various cases to analyze the effects of surface roughness and medium inhomogeneities. The results have shown that both mechanisms reduce the coherent reflection and transmission coefficients, because of the generation of incoherent scattered fields which in effect are to disperse coherent energy. It is also interesting to note that the variation of the reflection coefficient near the critical angle presents distinctive characteristics for different scattering mechanisms, potentially allowing to identify the dominant one for a particular problem under consideration.