ASA 124th Meeting New Orleans 1992 October

3aAO17. Acoustic daylight: Theory and numerical simulations for an imaging system using ambient noise in the ocean.

John R. Potter

MPL 0238, Scripps Inst. of Oceanogr., Univ. California at San Diego, 9500 Gilman Dr., La Jolla, CA 92093-0238

Following a successful pilot experiment for the acoustic daylight concept, it is planned to build a multibeam device to form real-time moving images. In support of this design, it is important to investigate the expected performance as a function of object shape, composition, apparent size and the degree and orientation of anisotropy in the illuminating ambient noise field. With such a large number of variables in the operating environment, a simple scattering model is required for the problem to remain tractable. This paper begins with the Helmholtz--Kirchhoff integral and uses the Fraunhoffer approximation, evaluating the integral by stational phase. This closely parallels the work of Funk and Williams [D. E. Funk and K. L. Williams, J. Acoust. Soc. Am. 91, 2606--2614 (1992)]. The analytic result is then summed numerically over ambient noise sources in a distributed field which result in specular scattering onto the receiver from a numerically specified surface. Some examples of simple analytic results and numerical simulations will be presented. [Work supported by the Office of Naval Research.]