Analysis of high-frequency acoustic scattering data measured in the shallow waters of the Florida Strait

Abstract

Experiments were conducted in the Florida Strait region of the United States in July 1995 to investigate the contribution of sediment volume scattering to measured acoustic backscatter levels at frequencies of 7.5 and 15 kHz. Five sites were analyzed for bottom backscattering level in the radial and azimuthal directions. Sediment geophysical parameters were established by a cross-well tomographic measurement and used as inputs for modeling. Both sediment volume and rough interface scattering models were utilized in analyzing the data. Comparison of model predictions with measured data showed that for grazing angles, at the water–sediment interface, from the critical angle to approximately 60 degrees, volume scattering dominated. For angles greater than approximately 60 degrees, surface roughness scattering consistently dominated. In geographic areas where the interface sound speed ratio exceeded one, roughness scattering controled the backscattered level for grazing angles less than the critical angle. Inversion of the measured acoustic backscatter data was performed using a genetic algorithm optimization developed for use with the volume scattering model. Inversion results were found to agree well with measured data and measured environmental parameters that describe the scattering volume.