BROAD-BAND MATCHED-FIELD PROCESSING

Acoustic energy in the ocean propagates from a source to an array of sensors via multiple pathways. Conventional time-delay-and-sum beamforming does not utilize energy contained in the multipath arrivals. In this paper, a generalized beamformer is presented which coherently recombines the multipaths to provide enhanced detectability of broadband transients as well as range and depth localization of the source. Modeling of the wave field at the array due to a broadband source is accomplished with a normal mode model using 1.0-Hz increments across the 1- to 100-Hz band. These results are combined to yield the impulse response from a specified source location to each of the array elements. The set of calculated impulse responses is used in the generalized beamformer to coherently recombine energy arriving along multipaths that exist from that source range and depth to the array. The location of a source is determined by examining the beamformer output at a number of candidate range/depth cells; a peak in the output gives the location of the source. Experimental data, consisting of multiple arrivals at a hydrophone array from an explosive source at mid-depth in 2800 m of water, are processed using the generalized-beamformer.