Blind deconvolution in ocean waveguides using artificial time reversal

Sound that travels through the ocean from a source to a receiver is commonly distorted by multipath acoustic propagation. The severity and details of this distortion are determined by the sound channel's characteristics, which may not be known. However, recovery or reconstruction of undistorted signals from recordings made in unknown complex multipath environments-a process commonly referred to as blind deconvolution-is advantageous in many applications of underwater acoustics. This paper presents a simple and robust means to achieve blind deconvolution in unknown sound channels with an array of receiving transducers. The technique, artificial time reversal (ATR), can be effective when there is a linear relationship between frequency and the phase of the low-order propagating modes of the sound channel. Broadband simulations of ATR in a generic shallow ocean sound channel show that the maximum correlation between the original signal and the reconstructed signal may approach 100% for signal pulses having a 258 Hz bandwidth and a 500 Hz center frequency. Application of ATR to ocean sound-propagation measurements produces original-to-reconstructed signal correlations from 80% to 95%. Possible extensions and improvements of ATR are discussed. (C) 2004 Acoustical Society of America.