Horizontal coherence of sound propagation in the presence of internal waves on the New Jersey continental shelf

Abstract

The knowledge of spatial coherence of sound field is required for sonar application and array design. In shallow water waveguides, the spatial and temporal evolution of the temperature field induced by internal waves will cause signal fluctuations and variations in spatial coherence. During the Shallow Water Acoustic Experiment 2006, the three dimensional temperature field of internal waves was measured and reconstructed while acoustic signals were simultaneously transmitted between various sources and an L-array. These internal wave events have been used to investigate the internal wave effect on temporal coherence and vertical structures of acoustic normal modes [Wan and Badiey, J. Acoust. Soc. Am. 135, 2014]. In this paper, the horizontal structures of acoustic normal modes are examined. The arrival angles of normal modes are analyzed. The horizontal coherence of sound field is obtained at different frequencies for these internal wave events. The relationship between horizontal coherence and internal wave parameters, such as propagation direction, speed, and amplitude, is discussed. [Work supported by ONR322OA.]