Scattered Fields from the Ocean Bottom

Abstract

An experiment to determine the acoustic field scattered from the bottom has been conducted in the Blake Plateau. Pulsed 19.5-kc/sec transmissions, directed toward the bottom, were made from a submarine as it approached and passed three special radio sonobuoys. 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° source beam incident on the bottom at grazing angles between 15° and 90°. The data were analyzed on the basis of an isotropic-scatter model. The velocity gradient was taken into account in the computation of the propagation. Results of the spatial field are presented in polar form in terms of the scattering strength. When integration over the scattered field is performed, the ratio of power scattered from the botom to incident power shows a decrease as the incident grazing angle is decreased from normal incidence. This implies that the loss of acoustic energy into the bottom is increased as the incident grazing angle is decreased in the range investigated.