Sound attenuation coefficients in sandy and silty seabottoms from low‐ to mid‐frequency field measurements in shallow water.

Abstract

The debate on the sound speed dispersion and the frequency dependence of sound attenuation in sediments has persisted for decades, mainly due to the lack of sufficient experimental data in the low‐ to mid‐frequency speed/attenuation transition band and the limitations of existing models. This paper analyzes and summarizes the LF measurements, conducted at 20 locations in different coastal zones around the world, that have resulted in the identification of nonlinear frequency dependence of sound attenuation in sand‐silt seabottoms for a frequency range of 50–2000 Hz [Zhou and Zhang, J. Acoust. Soc. Am. 117, 2494 (2005); 119, 3447 (2006)]. The resultant LF sound speed and attenuation can be described equally well by the Biot‐Stoll model, the Chotiros BICSQS model, and the Buckingham VGS model. However, a combination of the LF field‐inverted sound speeds and attenuations with data from the SAX99 and SAX04 measurements over a broadband of 50–400 000 Hz cannot simultaneously be matched by any of these models with one set of adjustable input parameters; these models either underestimate broadband dispersion or overestimate LF attenuation. Comments on the LF field‐derived data, such as “speed‐attenuation coupling,” are made. The possible reasons for the broadband data‐model mismatch are discussed. [Work supported by the ONR.]