Near-field blind deconvolution in a reverberant environment

Abstract

Artificial time reversal (ATR) is a passive technique for blind deconvolution in an unknown multipath environment that relies on generic features of underwater sound fields. ATR has been found to be effective when the source is far from the receiving array and the receiving array properly resolves propagating modes or ray-path arrival angles throughout the bandwidth of the source signal. This presentation describes the results of an experimental investigation into ATR's performance for a near-field source in a highly reverberant environment. The experiments were conducted with nominally 0.1 ms pulses at frequencies from 20 kHz to 150 kHz in a 1.0-m-deep and 1.07-m-diameter cylindrical water tank having a reverberation time of ∼10 ms using a single sound projector and a linear receiving array of 16 hydrophones. The correlation coefficient between the original and the ATR-reconstructed signals is presented as a function of receiving-array and broadcast-signal characteristics and compared to equivalent signal reconstruction results from spherical-wave delay-and-sum beamforming. The intended application of this research lies in determining the acoustic signature of cavitation bubbles and other hydroacoustic sound sources in hydrodynamic test facilities. [Sponsored by ONR and by NAVSEA through the Naval Engineering Education Center.]