ANALYSIS OF ACOUSTIC BACKSCATTER IN THE VICINITY OF THE DRY TORTUGAS

Experimental measurements of the bottom backscattering strength from c arbonate sediments were made with a 200-kHz multibeam sonar mounted on a remotely operated vehicle. Results were obtained from eight differe nt sites, which may be grouped into three categories, labeled soft, me dium and hard, according to measured sediment sound speed. Sediment sa mples were gathered at or near each site to help interpret the acousti c results. The acoustic results are compared with extant published dat a and with the BOGGART bottom backscatter model. Backscattering streng th values measured in the soft and medium sites fell within the main c luster of previously published values from sediments of similar grain sizes. The values from the hard region fell close to the upper limit. Dependence of the apparent backscattering strength on sonar height abo ve bottom, particularly for the lower values of height above bottom: w as observed, which suggests that the scattering process is a multiple- scattering one.