Temporal coherence of acoustic signals in range dependent background

Abstract

Temporal coherence of acoustic signals is important for many practical applications, which has been studied both theoretically and experimentally. In previous theories, the fluctuation of sound speed field is assumed to be caused by linear random internal waves and the background is assumed to be range independent. This assumption has two obvious shortcomings: (1) actual fluctuations in shallow water are usually modulated by internal tides; (2) seabed has significant effects on acoustic signal propagation in shallow water, the properties of which is, in general, range dependent (such as topography). In the present presentation, internal tides and seabed properties are involved as the range dependent background, in which the background acoustic field is expressed as coupled mode matrix. A semi-analytic formalism for the temporal coherence of acoustic signal is presented. The dependence of temporal coherence on range and frequency, and the impact due to range-dependence is analyzed. The result is compared with the case range-independent.