Extraction of both bottom backscattering strength and reflection loss by inversion of reverberation measurements

Abstract

A method is described to simultaneously extract the bottom backscattering strength and bottom reflection loss as a function of grazing angle from measurements of monostatic reverberation. The least-squares difference between a parametrized model and data is minimized with respect to the parameters using generic algorithms or simulated annealing. The reverberation data are from broadband sources and omnidirectional receivers deployed at a flat-bottomed deep-water area in the Mediterranean. The reverberation model is simple: the propagation is described by straight-line ray paths (although the effective angles are corrected for the sound-speed profile); and parametrized functions are used for the bottom scattering strength and reflection loss. The parameters can also include the water depth, sound speed and gradient, source level, and pulse length. Where they can be compared, the parameters resulting from the inversion show good agreement with the measured ones, leading confidence to the procedure. As well, when the resulting parameters and actual sound-speed profile are input to the generic sonar model, the calculated and measured reverberations are in good agreement. a)Currently at Rijkswaterstaat, P.O. Box 3006, 2280MH Rijswijk, The Netherlands.