Dept. of Appl. Ocean Phys. and Eng., Woods Hole Oceanograph. Inst., Woods Hole, MA 02543
This is a model of shallow-water reverberation due to sediment volume inhomogeneities. The scatterers are three-dimensional sound speed and density variabilities in the sediment. A first-order perturbation approximation is adopted assuming the sediment variabilities are small quantities. Within the applicable range of that approximation, this formalism is exact. It is found that the strength of the scattered field or reverberation strength can be expressed as the coupling between the incident and scattered normal modes. The mode coupling coefficient is found to be the same as the scattering coefficient sampled at relevant modal angles. In the development of the formulation, no empirical scattering function is involved. Also found is a dispersion factor associated with each mode in the mean reverberation curve corresponding to the spreading of the source pulse for each mode. Numerical examples are given for typical shallow-water environments.