Effect of Sub-Bottom Inhomogenieties on Shallow Water Spatial Coherence
A coupled-mode approach is applied to examine the spatial coherence of the acoustic field in an inhomogeneous waveguide. The formulation derived is a matrix analog of the equations resulting from application of strong fluctuation theory to propagation in an inhomogeneous medium. The expression that results is evaluated to determine the effect of sub-bottom roughness on horizontal spatial coherence in shallow water. Results are presented for low-frequency propagation in an environment in which a homogeneous clay-silt sediment overlies irregular bedrock. Numerical examples demonstrate the effects of frequency, water depth and source-receiver geometry on coherence. For the cases examined, the field is coherent over many wavelengths in qualitative agreement with existing data.
KeywordsCoherence Explosive Acoustics Hydrophone
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