Three-Dimensional Scattered Fields from the Ocean Bottom

An experiment to determine the three-dimensional acoustic field scattered from the sea bottom was conducted in the Blake Plateau. Pulsed 19.5-kHz transmissions were directed toward the bottom from a submarine as it approached and passed three special radio sono-buoys. The buoys were spaced to provide the maximum coverage of the scatter field in the half space above the bottom. Reception was made at each of the three buoys and at the source transducer. Sets of data were taken with the axis of the 8 degrees source beam depressed at angles between 15 and 90 degrees. The data were analyzed on the basis of an isotropic scatter model. Results of the spatial field were plotted in polar form, in terms of the mean scattering strength. When integration over the scattered field is performed, the ratio of power scattered from the bottom to incident power is unusual in that it is low at both low and high incident angles. The experiment resulted in the most comprehensive set of measurements of the bottom-scattered field yet obtained. (Author)