ASA 127th Meeting M.I.T. 1994 June 6-10

1pUW14. Seafloor backscattering from explosive sources during the 1993 Mid-Atlantic Ridge experiment: Preliminary results.

J. M. Berkson

Naval Res. Lab., Washington, DC 20375

G. L. Gibian

J. Richardson

Planning Systems, Inc., McLean, VA 22102

During the Acoustic Reverberation Special Research Program (ARSRP) acoustic experiment of July 1993, an experiment was performed to identify seafloor scattering mechanisms. Explosive SUS sources were deployed on the western flank of the Mid-Atlantic Ridge to provide omnidirectional broadband sound for long-range reverberation measurements. In addition, pulsed cw tones in the frequency band 200 to 280 Hz from a vertical source array were used. The signals scattered by the seafloor were received by two 64-wavelength subapertures of a towed array, processed to form beam-time series, and then displayed as reverberation images on map projections. In order to obtain good signal-to-noise ratios, this analysis was performed in frequency bands of 4 Hz (time resolution 0.25 s) and then averaged to form beam-time series of 20-Hz bandwidth at harmonics of the bubble-pulse frequency. Initial results show that the cw measurements are consistent with the broadband results and that scattering strengths of specific seafloor features are generally constant over the frequency band 100 to 1000 Hz. [Work supported by ONR.]