Acoustic boundary wave generation and shadowing at a seamount.

Abstract

The interaction of a sound field and a seamount has been studied by physically modeling the ocean surface over 2 dimensional and 3 dimensional models of Dickens Seamount. By using a smooth ocean surface, and one with a surface of scaled Rayleigh roughness to model a 35 knot wind, the relative contributions are determined for off-axis scattering elements, multiple reflection from the ocean surface, and diffraction over the crest of the seamount. Boundary wave generation over a randomly rough plane surface is studied experimentally. The ratio of boundary wave amplitude to volume wave amplitude is found to be proportional to (frequency) ³/² and (range) ¹/² and the ratio of the empirical scattering parameter to the rms height of the roughness elements is found to be approximately 0.3. The spatial correlation length of the randomly rough surface takes the place of the center-to-center separation of the hemispherical bosses used in Tolstoy's theoretical treatment.