Processing of reverberation data from 400–3500 Hz using line arrays with left/right discrimination

Abstract

The author recently participated in two experiments using directional towed arrays. One was the 2004 boundary characterization experiment near the Malta Plateau. That experiment was led by the NATO Undersea Research Centre (NURC). The area is rich in clutter objects like wrecks and mudvolcanoes and has some sub-bottom features that may be important. Sources were monostatic coherent pulses and SUS. The receiver was the NURC cardioid array. The other experiment was ONR’s 2003 Geoclutter effort to study shallow-water bottom reverberation and clutter in the STRATAFORM off New Jersey. That experiment was led by M.I.T. Sources were bistatic coherent pulses. The receiver was the five-octave research array (FORA). The STRATAFORM is known to have benign surface morphology but strong clutter is observed. Some highlights of the reverberant returns are discussed that include the correlation of returns with manmade targets and probable fish schools. The purpose of this work is to assess the directional characterization of the observed clutter and reverberation. The cardioid arrays should yield good directional estimates of reverberation sources above ∼1600−1800 Hz. Examples from the data analysis are presented using a cardioid beamforming algorithm developed by NURC. [Work supported by ONR Code 32, Grant N00014-03-1-0113.]