The frequency dependence of attenuation in marine sediments is investigated using in situ measurements from a wide-band acoustic probe system during the Shallow water 2006 (SW06) experiment. Direct-path pulse propagation measurements within the 10-80 kHz frequency band show linear frequency dependency of attenuation in dB/m at two silty-sand sites on the New Jersey Shelf. The measurements also show evidence of mild velocity dispersion within the 10-80 kHz frequency band. The measured attenuation and velocity dispersion curves are in good agreement with those predicted by an extended Biot theory for sediments with a distribution of pore sizes [Yamamoto and Turgut, J. Acoust. Soc. Am. 83, 1744-1751 (1988)]. Attenuation roll-off measurements (dB/m kHz) were also conducted within a 3-8 kHz frequency band using chirp-sonar subbottom profiler. The comparable levels of attenuation roll-off are observed from the chirp sonar and acoustic probe measurements. [Work supported by ONR.]

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