ASA 124th Meeting New Orleans 1992 October

5aUW1. Long-range reverberation from the seafloor in the Mid-Atlantic Ridge area.

J. M. Berkson

N. C. Makris

R. Menis

M. R. Healey

Naval Res. Lab., Washington, DC 20375

G. L. Gibian

Planning Systems, Inc., McLean, VA 22102

Long-range measurements of reverberation from the seafloor were made in the Mid-Atlantic Ridge area during the Acoustic Reverberation Special Research Program Reconnaissance Experiment in August 1991. Sound from a low-frequency source array at 210 to 290 Hz was scattered by the seafloor at basin-wide ranges and then received by a towed array. Reverberation images show strong returns in the direct-path region followed by strong returns within concentric bands corresponding to bottom convergence zones. Diffuse and discrete returns occur in both regions. Reverberation images from HFM pulses of differing frequency exhibit similar behavior as do CWs. Discrete features exhibit constant or decreasing relative reverberation level with frequency. Cross correlation between reverberation beam/time series for different frequency CW subpulses over these features exhibited high but variable correlation throughout the band. [Work supported by ONR.]