ASA 129th Meeting - Washington, DC - 1995 May 30 .. Jun 06

2aUW20. Broadband guide source helps localization in shallow water.

Appl. Phys. Lab., Univ. of Washington, Seattle, WA 98105

Acoustic measurements from a broadband guide source are used in a highly variable shallow ocean to augment sparse environmental information. The concept of using a broadband guide source is inspired by the astronomical technique in which light from a star is used to correct atmospheric aberration of a nearby (in the angular sense) object. The acoustic technique investigated here is similar to holography [P. D. Mourad et al., 1031--1039 (1992)] in which a vertical array of continuous wave (cw) reference sources is used to localize unknown targets by reconstructing the wavefront at the location of the reference source array, removing much of the distortion caused by the ocean. Mourad et al. showed that this method is effective where the adiabatic approximation is valid. The present technique differs by using a single broadband guide source in shallow water where mode coupling can occur. In this work, we develop a method similar to holography valid for strong range-dependent environments, together with single hydrophone matched field methods to solve the source localization problem. Numerical simulations are also given for a variety of environments to demonstrate the effectiveness of the method. [Work supported by Office of Naval Research.]