Small Grazing Angle Reverberation Vertical Correlation in Shallow Water

Abstract

Reverberation is a superposition of echoes from scatterers at one time. All the scatterers distribute in oceans randomly, which makes reverberation as a stochastic process, while it also has clear space correlation characteristic, which is an important characteristic of reverberation. Reverberation vertical coherence characteristic had to be considered for active sonar design. In this paper, long range reverberation vertical correlation model has been made based on bottom reflection coefficient model parameters and smooth average sound field approximation in shallow water, which make normal modes composition into angular integration. Smooth average sound field approximation reveals that normal mode at source and receiver depth can approximate as a function of cycle distance. Bottom reflection coefficient model proposes that normal mode at water-sediment interface as a function of reflection phase parameter and normal mode attenuation can be described by amplitude parameter directly. Such theory model shows that there is a clear relationship between reverberation vertical correlation and bottom reflection coefficient amplitude and phase parameters, and such relationship varies with scattering range and vertical separation. In Pekeris waveguide, simulation also illustrates that reverberation vertical coherence is much sensitive with phase parameter than amplitude parameter.