Coherence estimates for signals propagated through acoustic channels with multiple paths

Theoretical estimates of space, time, and frequency coherence are obtained for a sound field generated by a moving source and observed at a stationary array of sensors. It is shown that spatial coherence depends principally upon the spread of ray‐path‐arrival angles at the receiving sensors and on the orientation of the receiving array to the sound field. Temporal coherence depends upon the ray‐path angle spread at the source and on source motion. Oscillatory source motion introduces frequency modulation of the transmitted signal with sideband levels related to projector displacement amplitude. Frequency coherence depends upon the time spread between arrivals which propagate over different acoustic paths. Examples of theoretical coherence functions are presented for multipath channels of interest in underwater acoustics.