On the sound speed dispersion and the frequency dependence of sound attenuation in a fine-grained sediment in the New England Mud Patch

The study on the sound speed dispersion and the frequency dependence of sound attenuation in marine sediments is of great importance in understanding the physics of sound propagation in the sea bottom. Modal dispersion curves (MDC) have only been utilized to estimate the low-frequency sound speed. At higher frequencies (i.e., above a few hundred hertz), arrival time difference for different modes generally become smaller and MDC is difficult to extract because of the cross-mode interference. This paper applies time-frequency representations (TFR) with high time-frequency resolution (e.g., optimal-kernel and center-affine-filtered TFR) to broadband acoustic signals (e.g., 31g explosive and combustive source signals) detonated along the 15-km Northwest-Southeast tracks during the Seabed Characterization Experiment in the New England Mud Patch, which has a surface fine-grained sediment layer overlying a sandy bottom. The resulting high-resolution broadband (150–1500 Hz) MDC, in conjunction with TL data, are fed to a previously developed two-step dimension-reduced geoacoustic inversion algorithm including modal dispersion-based inversion for sound speed and energy-based inversion for attenuation [IEEE J. Ocean. Eng., 44, in print, (2019)]. The estimated sound speed and attenuation are compared with the theoretical results from seabed geoacoustic models for fine-grained sediments. [Work supported by ONR Ocean Acoustics (322OA).]The study on the sound speed dispersion and the frequency dependence of sound attenuation in marine sediments is of great importance in understanding the physics of sound propagation in the sea bottom. Modal dispersion curves (MDC) have only been utilized to estimate the low-frequency sound speed. At higher frequencies (i.e., above a few hundred hertz), arrival time difference for different modes generally become smaller and MDC is difficult to extract because of the cross-mode interference. This paper applies time-frequency representations (TFR) with high time-frequency resolution (e.g., optimal-kernel and center-affine-filtered TFR) to broadband acoustic signals (e.g., 31g explosive and combustive source signals) detonated along the 15-km Northwest-Southeast tracks during the Seabed Characterization Experiment in the New England Mud Patch, which has a surface fine-grained sediment layer overlying a sandy bottom. The resulting high-resolution broadband (150–1500 Hz) MDC, in conjunction with TL data, are ...