Effects of random bottom structure and topography on transmissions in a shallow ocean

Abstract

In a recent paper [C. E. Ashley, M. J. Jacobson, and W. L. Siegmann, J. Acoust. Soc. Am. 76, 1445–1455 (1984)], the authors studied the influences of stochastic horizontal bottom structure on underwater sound transmissions. Both bottom density and sound speed were taken to be random. Ray theory was used in an isospeed channel with horizontal boundaries. In this study, we add to random structural effects those of a lossy bottom interface consisting of large-scale random facets with curvature, on which may be superimposed small-scale roughness. Each facet is assumed to possess small random slope, depth deviation, and curvature. Initially, we take acoustic rays to be specularly reflected from a large-scale facet bottom, and derive formulas for the mean and variance of incoherent intensity at a point receiver for a transmitted cw signal. The results are sufficiently general to permit their use with different bottom-acoustic models. Relative effects of structure and topography are compared. Subsequently, small-scale roughness is added to the facets, and the consequences of scattering are considered. [Work supported by ONR.]