Study of Shallow-Water Reverberation Spectra with Spatially Offset Signal Transmission and Reception Points

In this article, we study the characteristics of reverberation interference that occurs in a marine environment when long tonal pulses are emmited and scattered signals are recorded using the so-called bistatic scheme, i.e., when the receiver is located a large distance from the transducer. Probing of the water area with tonal pulses is carried out with the necessary resolution to study both the Doppler spectrum, and temporal development of the reverberation signal is achieved by selecting the proper pulse length. The presented theoretical model is applicable to both the direct and inverse problems, which are forecasting the characteristics of reverberation for a given sea state and determining the properties of the marine environment, mainly its near-surface layer, based on the results of acoustic sounding. The model represents a scattered signal as the superposition of reflections from scatterers, which are distributed along the depth and move along circular trajectories. Their speeds are determined by the maximum amplitude and period of wind waves. The article continues a series of studies and generalizes the previous results to the conditions of significantly spatially offset sound sources and receivers. The modeling results are confirmed by experimental data, involving such parameters as the width of the Doppler spectrum and law of decay of reverberation intensity over time.