Fluctuating three dimensional acoustic wave propagation in shallow water present challenge due to the anisotropic nature of the environment. Temporal and spatial changes in the water column caused by the passage of internal waves are among the primary causes of the anisotropy. Three main mechanisms for the acoustic field variations have been determined: 1) adiabatic propagation, 2) horizontal refraction, and 3) mode coupling. All these mechanisms provide different characteristics of the sound fluctuations, and depend on the angle between the internal wave direction and the source receiver propagation path, as well as frequency and mode number. In a recent multi-institutiol shallow water experiment (SW06) a series of source-receiver positions were created to examine the effects of 3D environmental fluctuations on the propagation of low to mid frequency (0.05-3kHz) broadband acoustic signals while extensive enveronmental observations were made. These recent observational results confirm the above theoretical hypothesis. Work supported by ONR-321OA and RFBR

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