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Geoacoustic inversion using vector acoustic modal dispersion

Geoacoustic inversion is traditionally performed using sound pressure data. Here, we present a study of geoacoustic inversion using particle velocity, as recorded on a vector sensor. The scope of the study is restricted to shallow water and low-frequency impulsive sources. In this context, the propagation is described by normal mode theory. The modal description of the vector field is well known: the mode amplitudes are different than from the pressure field, but their phase is the same. As a result, modes can be filtered from particle velocity data in the same way that they are filtered from pressure data, as long as one considers filtering methods that are based on the modal phase. We show that warping (a non-linear resampling scheme) enables modal filtering on both pressure and particle motion data. Then, the filtered modes (pressure and velocity) are coherently combined to form four vector acoustic metrics [Dahl and Dall’Osto, IEEE J. Oceanic Eng. 2019]. Each metric is used as an input for Bayesian geoacoustic inversion. The whole method is illustrated on a simulated scenario that reproduces the Seabed Characterization Experiment (SBCEX) that took place on the New England Mud Patch in 2017. [Work supported by the Office of Naval Research.]