Estimation of sound speed and attenuation in mud sediments using combustive sound source signals measured on the New England continental shelf

Abstract

Acoustical measurements were made in coincidence with an environmental survey for future sediment characterization experiments in the mud patch region of the New England continental shelf from July 22 to August 3, 2015. One vertical line array (VLA) containing six hydrophones and 15 environmental sensors was deployed in 75-m water at the center of the survey (40.477o, −70.604o) in order to record noise data and the acoustic signals generated by the combustive sound source (CSS) [McNeese et al., J. Acoust. Soc. Am., 2014]. Fifteen CSS shots detonated at various ranges (2.5 km and 14.5 km) and depths (5 m, 10 m, and 20 m) were recorded by the VLA. The sub-bottom layering structure with a mud layer overlaying a sand bottom was obtained from the CHIRP sonar survey. This paper utilizes the modal dispersion characteristics to invert the sound speed in the bottom. Then, the sound attenuation in mud as a function of frequency is estimated using the transmission loss (TL) data. Measured modal dispersion curves are compared with modeled dispersion curves based on the inverted bottom acoustic parameters. [Work supported by ONR.]