Calibrated bistatic Rayleigh-born bottom reverberation model for fluctuating range-dependent continental shelf environments

Ameya Galinde, Northeastern University
Ninos Donabed, Northeastern University
Purnima Ratilal, Northeastern University
Sunwoong Lee, Massachusetts Institute of Technology
Nicolas Makris, Massachusetts Institute of Technology

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Poster presented at the 2007 Validating TestBED and Research on Real World Problems for I-PLUS Development Conference

Abstract

Analytic and numerical models are developed for reverberation from volumetric inhomogeneities in the sea bottom in range dependent ocean waveguides using the Rayleigh-Born approximation to Green's theorem. The expected reverberation intensity depends on the statistical moments of the fractional changes in compressibility and density, which scatter like monopoles and dipoles respectively, and the coherence volume of the inhomogeneities. The model is calibrated using data acquired with a long range sonar on the New Jersey continental shelf during the 2003 Main Acoustic Experiment of the ONR Geoclutter Program. An approach for distinguishing moving clutter from statistically stationary background reverberation in long range sonar imagery is developed. Geoacoustic parameters needed for the calibration are either derived from previous geophysical surveys of the region or estimated from reverberation data. Analysis with the model indicates that the scattering strength of the bottom on the New Jersey shelf is approximately -37 1 dB re 1m. An approximate but computationally efficient numerical approach is also developed to simulate reverberation over wide areas for operational sonar syatems. The numerical model employs the Navy standard range-dependent propagation model based on the parabolic equation, RAM, and can be readily incorporated into current Navy systems. Model is applied to minimize bottom reverberation and enhance biological detection for OAWRS imaging of fish.