Trans-dimensional inversion for sediment attenuation using modal dispersion data collected by an underwater glider

Abstract

This paper inverts modal-dispersion data collected by an underwater glider to estimate a layered seabed geoacoustic model including sediment attenuation as well as sound speed and density. The data considered here were collected during the 2017 Seabed Characterization Experiment (SBCEX17) conducted on the New England Mud Patch. The distance between the (combustive) sound source and the hydrophone-equipped (Teledyne Webb Research Slocum) glider was approximately 8 km. The frequency range considered was from 20 to 392 Hz, and 6 modes were resolved from the data using warping. Previous work has demonstrated that the positions of dispersive acoustic modes in the time-frequency plane provide information to estimate seabed sound-speed and density profiles. Including the relative energy distribution in the time-frequency plane (normalized modal amplitudes and/or amplitude ratios between modes) provides additional information to also estimate sediment attenuation, which is carried out here using a trans-dimensional Bayesian inversion. In addition, uncertainties of the seabed sound speed and density with/without modal energy information are compared. [Work supported by ONR.]