Acoustic Blind Deconvolution in Uncertain Shallow Ocean Environments

Abstract

Abstract : The overall long-term goal for this project is to develop engineering tools that are useful to the Navy as it operates in uncertain, partially-known, or unknown ocean environments. During the last year, this project has focused on further determining the utility of a time-reversal-based technique for blind deconvolution of recorded sounds broadcast by a remote source with emphasis on determining if and how the results might be used for tracking and identification of remote sources in poorly known or unknown ocean waveguide environments. The long term goals of this project since are: 1) to determine the effectiveness of artificial time reversal (ATR) for the purposes of blind deconvolution in noisy unknown ocean sound channels, 2) to effectively apply ATR to marine mammal sounds recorded in the ocean with vertical and/or horizontal arrays, and 3) to utilize the ATR-corrected signals and ocean-sound-channel impulse response estimates to identify and track individual marine mammals (or other sound sources of interest). Since early 2009 this project has focused on developing an acoustic-ray-based version of artificial time reversal (ATR), a technique for recovering the original signal and the source-to-array impulse response for a remote unknown sound source in an unknown ocean waveguide. The specific objectives are to: a) determine the signal-to-noise, array size, and array element number limitations of ATR via acoustic propagation simulations, b) verify these findings with simple airborne-sound laboratory experiments involving multiple microphones and several ray paths, c) obtain and process at-sea array recordings of remote-but-cooperative sound sources, and d) obtain and process marine mammal vocalizations for the purposes of marine mammal tracking and identification. This research effort extends the past mode-based version of ATR to higher frequencies and smaller receiving arrays, and will identify its capabilities and limitations.