Determination of frequency dependence of sediment attenuation in shallow water using the combustive sound source

Abstract

Acoustic signals generated by the combustive sound source (CSS), an impulsive source based on hydrogen‐oxygen combustion, were recorded at various source‐array ranges on two L‐arrays during the Shallow Water’06 experiment off the coast of New Jersey, in about 70 m of water. The bandwidth of the CSS is about 3 kHz and thus offers an opportunity to determine those geo‐acoustic parameters of the seabed that are frequency dependent. One parameter that has received significant attention is the sediment attenuation due to its importance in correctly predicting transmission loss in shallow water. In principle, if one can determine the real part of the sediment sound speed and layering structure, the received acoustic data over a 3 kHz band could be used in combination with an advanced propagation model to determine the frequency dependence of the sediment attenuation. The central hypothesis of the study is that while such an inverse approach is subject to non‐uniqueness, a significant number of physical measurements such as the sound speed profile in the water column, bathymetry, and sub‐bottom layering that were made along the propagation paths may provide adequate constraints that allow for a unique determination of the sediment attenuation. [Work supported by ONR.]