Seabed attenuation inversion from broadband reverberation measurements in the Yellow Sea

Abstract

The Yellow Sea 1996 experiment was the first joint China-U.S. shallow water experiment conducted in August, 1996. The water depth is 75 m with a deviation of ±1 m at the experimental area. The seabed sound speed and attenuation in this experiment have been successfully estimated using the sound propagation measurements [Wan, Zhou, and Rogers, J. Acoust. Soc. Am. 128(2), 2010]. During this experiment, the monostatic reverberation data produced by 1-kg TNT shots provide a spatial sampling of the acoustic field and contains the information of seabed acoustic properties. Thus, the present paper uses the inverted seabed sound speed from the aforementioned propagation measurements as a constraint condition and analyzes the reverberation data for seabed attenuation inversion. The broadband normal mode filter is applied to the reverberation data received by a 32-element vertical line array. The reverberation level of the first three modes is obtained as a function of range to extract the modal attenuation coefficients. The seabed attenuation is inferred by minimizing the difference between the theoretical and measured modal attenuation coefficients. The inverted seabed attenuation over a frequency range of 400–1000 Hz shows non-linear frequency dependence.