ACOUSTIC-WAVES IN A SHALLOW INHOMOGENEOUS OCEAN WITH A LAYER OF SEDIMENT

This paper deals with the direct underwater acoustics problem for a he terogeneous ocean of uniform depth with an acoustically interacting un iform layer of sediment. The acoustic properties of the ocean column a re assumed to vary only with depth. Using the standard boundary condit ions, i.e. a pressure release surface, continuity of normal stress and displacement across the ocean-seabed interface, and Sommerfeld type r adiation conditions, we are able to determine the acoustic far-field u sing normal modal expansions. The nonhomogeneous character of the ocea n is conveniently handled using transmutation theory. Transmutation th eory yields an explicit form for the characteristic equation, and in a ddition, an appropriate inner product for the composite Sturm-Liouvill e system. The Fourier coefficients for the expansion of the propagatin g fundamental solution is also obtained. A numerical scheme is present ed and several examples are given.