Acoustic Blind Deconvolution and Frequency-Difference Beamforming in 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 fully-passive propagation-physics-based technique for blind deconvolution of array-recorded sounds from a remote source with emphasis on determining how sparse-array measurements might be used for this task. The long term goals of this project are: i) to determine the effectiveness of synthetic time reversal (STR) for the purposes of blind deconvolution in noisy unknown ocean sound channels, ii) to effectively apply STR to marine mammal sounds recorded in the ocean with vertical and/or horizontal arrays, and iii) to utilize the STR-estimated signals and ocean-sound-channel impulse responses to classify, localize, and/or 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 synthetic time reversal (STR), a fully-passive technique for recovering the original signal and the source-to-arrayelement impulse responses for a remote unknown sound source in an unknown underwater waveguide [1-4]. The specific objectives are to: a) determine STR performance as a function of the signal-tonoise, array size, and array element number using acoustic propagation simulations, b) verify these findings with simple airborne- or water-borne acoustic laboratory experiments involving multiple receivers and multiple ray paths, c) obtain and process underwater array recordings of remote-butcooperative sound sources, and d) obtain and process marine mammal vocalizations for the purposes of marine mammal localization, tracking, and identification. This research effort extends the prior modebased version of STR [1] to higher frequencies, smaller receiving arrays, sparse receiving arrays, and sound channels with modal dispersion