Passive time-reversal mirror for acoustic characterization of the seabed

This paper investigates application of a signal processing technique, which is motivated by time reversal, to geoacoustic inversions in a shallow-water waveguide. The signal processing mimics operation of a physical time-reversal mirror. The input data for the simulated time-reversal mirror can be obtained using either a compact, broadband sound source or cross-correlation of the diffuse noise recorded by spatially separated receivers. Low-frequency sound propagation is considered over ranges that are large compared to the water depth. The approach exploits the notion that the “best” focusing of the backpropagated time-reversed signal occurs at the “right point,” when the backpropagation takes place in the same propagation medium as the one, where the data have been acquired. Various metrics of the focusing quality are considered. A combination of spatial and temporal characteristics of the focus is proposed that leads to a unique solution of the geoacoustic inverse problem for a single-element passive time-reversal mirror. [Work supported by NSF.]