Scattering of Sound by Internal Waves: The Role of Particle Velocities

Abstract : Internal waves scatter sound by two related perturbations: (1) those associated with vertical particle displacements zeta (x, y, z, t) in the presence of a vertical gradient of (potential) sound speed: delta times c = zeta. gamma sub z c sub p; (2) those associated with horizontal particle velocities u(x, y, z, t). The combined perturbations in refractive index are delta times c/c + u/c. The second term, which has been generally neglected, does become important under two rather special circumstances: (a) in sound transmission along a deep downward loop, and (b) in the difference between transmission from a source at point A to a receiver at point B and transmission from a source at b to a receiver at A.