ASA 128th Meeting - Austin, Texas - 1994 Nov 28 .. Dec 02

3aUW10. High-frequency sound variation in a coastal environment.

Jules S. Jaffe

Marine Phys. Lab., Scripps Inst. of Oceanogr., La Jolla, CA 92093-0238

Despite the proliferation of high-frequency sonar imaging systems, the variability of high-frequency sound propagation in shallow water has only recently been measured. In a series of experiments adjacent to the Scripps Institution of Oceanography pier, the variability of sound at a frequency of 450 kHz has been measured. The experimental measurement consisted of deploying a multibeam imaging system on a tripod in approximately 20 ft of water. Repeated insonification and subsequent measurement of the backscattered waveforms indicate that a large degree of variability can exist in the backscattered data. In order to define whether the source of the variability in the backscattered data was originating from the bottom or the volume, a corner reflector was deployed. Assuming that the variability in the sound reflected from the bottom consists of the superposition of both volume and the bottom variability, and that the sound from the corner reflector consists of variability only from the volume, assignment of the relative importance between the two forms of variability can be made. The importance of these two sources of variability as a function of environmental conditions such as tide and surface conditions will be presented. [Work supported by ONR.]