Acoustic point-source reflection from a seabed with a non-uniform fluid-like sediment layer

Abstract

Acoustic point-source reflection from a non-uniform seabed within which the density and sound speed vary continuously with depth is considered in this paper. This fundamental problem has illuminated many interesting phenomena about the effects of sediment stratification on acoustic wave interactions with the seabed. The analysis employs the analytical solutions for the Helmholtz equation in the sediment layer, in which the density and the sound speed are, respectively, described by three kinds of geological models. The results have demonstrated that the effects of sediment stratification are confined in a region in range, where the reflection field is dominated by the reflected ray bundles containing ray components with the grazing angles that are neither too steep nor too shallow. The effects of many other factors, such as frequency, sediment thickness, basement elasticity, on the reflection field are investigated; in particular, the interface wave component may become important in the region close to the sea-bed, if the sediment thickness is relatively thin in comparison with the acoustic wave length