Abstract:

Inverse beamforming (IBF) has been developed over the last decade by the authors, and has proved highly successful in numerous at-sea tests. IBF is a unique signal processing method because the noise field properties are first determined by inverse techniques as a function of frequency, azimuth, magnitude, and the ``widths'' of these three dependent variables. The statistical properties of the noise field are determined, and a beam-forming algorithm and six-dimensional tracker were developed to reject the noise and pass the signal (whose properties are well studied). IBF applies to deep water only, and this paper addresses the development of a similiar noise rejection algorithm in shallow water. The shallow-water problem is more complex due to the normal mode propagation characteristics at low frequencies, and the diversity of noise mechanisms in shallow water. Noise measurements are critically needed in shallow water to validate this approach.