Shallow Water Temporal Coherence of Broadband Acoustic Signals in the Presence of Internal Waves

Abstract

Temporal coherence is closely related to single path phase rate. The single path phase rates in a shallow water environment were obtained by applying two different multipath models [Dyson, Munk, and Zetler, J. Acoust. Soc. Am., vol. 59, pp. 1121-1133, 1976 and Mikhalevsky, J. Acoust. Soc. Am., vol. 66, pp. 751-762, 1979] on simulated data with internal waves. The estimated phase rates were consistent between the two models. In contrast, previous application of the same models on deep water data showed a factor of 8 difference in their phase rates. The phase rates derived from the models become independent of range after a uniform phase distribution is reached in the (-/spl pi/,/spl pi/) region. The shallow water coherence time varies considerably with depth at a given range. The depth dependence is explained with a correlation function constructed with mode depth functions.