Some shallow water reverberation highlights and bottom parameter extractions in the 80–4000 Hz region from the boundary characterization and geoclutter experiments

Abstract

Together with SACLANTCEN, the authors recently participated in two trials to measure shallow water bottom reverberation near Sicily and the STRATAFORM off New Jersey. Sources were monostatic SUS charges and coherent pulses. The receivers were horizontal arrays. Data were analyzed in bands from 80 to 4000 Hz. Highlights of the reverberant returns are discussed. The STRATAFORM is known to have benign surface morphology but contains many buried river channels. One author was also involved in the 2001 Geoclutter experiment conducted in STRATAFORM using coherent bistatic sources near 400 Hz. Differences in reverberation characteristics between SUS and Geoclutter results are discussed. Another objective of these reverberation experiments was to quickly invert for scattering and geoacoustic parameters. A simulated annealing (SA) algorithm was used together with the Generic Sonar Model (NUWC). After automatically adjusting bottom loss and scattering strength, good agreement is achieved between the diffuse reverberation data and model predictions in relatively flat areas. Model/data differences are generally correlated with bottom scattering features. Since reverberation typically lasts 10–20 s or more, extracted parameters apply over wide areas. Local bottom loss and backscattering measurements were made by Holland in these areas. A comparison with Holland’s results is given. [Work supported by ONR Code 32, Grant No. N00014-97-1-1034.]