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.
KeywordsWater Depth Mode Coupling Acoustic Field Spatial Coherence Source Depth
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