Geoacoustic inversion of ocean surface-wave noise with a littoral glider.

Abstract

Passive acoustics can be used to characterize the ocean bottom in a littoral environment. Ocean surface-wave noise acts as a natural directional source that can be measured to obtain bottom loss and subsequently inverted to obtain bottom density, sound speed, attenuation, and layering structure. A physical ocean surface noise model is introduced and its horizontal/vertical spatial cross-correlations is discussed. Acoustical energy conservation and its relation to bottom loss are discussed. The measurement method is a continuation of the ambient noise inversion work of [J. I. Arvelo, Jr., J. Acoust. Soc. Am. 123, 679–686 (2008)]. Aggressive adaptive beamforming is used for high-resolution bottom loss measurements with surface-wave noise as a source. Ambient noise measurements with an eight-element wire polyvinylidene fluoride vertical line array mounted in the bow of a littoral glider are presented. Results from summer 2008 measurements in Port Madison, WA are presented and compared against known bottom loss curves for the area. [Work supported by SPAWAR.]