Sediment Acoustics: Wideband Model, Reflection Loss and Ambient Noise Inversion

(1) Consolidation of the new BIC08 model: The Biot-Stoll grain contact squirt flow and shear viscous drag (BICSQS) model, which includes squirt flow at the grain-grain contacts (Chotiros, Isakson 2004), combined with improvements in squirt flow modeling, the frame virtual mass extension to account for the random grains rotation (Chotiros, Isakson 2007), and the high-frequency viscous drag correction (Chotiros, Isakson 2008) form the Biot-Stoll contact physics model of 2008 (BIC08). This model contains plausible physical processes and is able to track the measured frequency dependence of sound and shear speed and attenuation in water-saturated sandy sediments. In its present form, it is too unwieldy for practical applications. The approach is to consolidate the input parameters and reduce the parameter count, to continue to test it against experimental measurements and extend it to a wider variety of ocean sediments. In support of the modeling, new experimentation methods are envisioned, including the exploitation of ambient noise for bottom characterization using a compact, partially buried array. Through participation in future shallow-water (SW11) and sediment acoustics experiments (SAXnn), further testing is planned with a wide range of sediment types and over a broadband of frequencies, to extract model parameter values that are typical for specific classes of sediments.