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

1pUW19. Seafloor insonification near the Mid-Atlantic Ridge.

Vincent H. Lupien

J. Robert Fricke

Dept. Ocean Eng., 77 Massachusetts Ave., Cambridge, MA 02139

As part of the Acoustical Reverberation Special Research Program (ARSRP), several at-sea experiments were performed near the Mid-Atlantic Ridge to understand low grazing angle backscattering from the ocean seafloor. Although the bathymetry for this region is known, the seafloor has not been classified into acoustically relevant types. In order to classify the seafloor according to its acoustical scattering properties, events in the backscattered signal must be co-registered with regions on the actual seafloor, and the propagation process must be modeled. A software package was developed that uses ray-tracing to yield the seafloor insonification patterns of receiving and transmitting arrays. This tool allows for arbitrary location and orientation of both arrays, an arbitrary sound-speed profile, and arbitrary beam patterns for both arrays. The end product is a set of surfaces representing the time delay, two-way transmission loss, and grazing angle (among other parameters) for each point on the known bathymetry. This step is key in extracting acoustical scattering types from the receiver signals. It is anticipated that the method will permit better utilization of the available data since sidelobe radiation is not neglected. [Work supported by ONR.]