Spatial coherence in shallow water

For applications such as beamforming and matched field processing, it is important to understand spatial characteristics of shallow water acoustic fields. Oceanic and geoacoustic variabilities introduce random fluctuations into the fields, for which an important characteristic is the spatial coherence. The spatial coherence of the acoustic field is described by the correlation function of the field. Results from a careful investigation are described of the sensitivity of the correlation function to variations in parameters of shallow water propagation. Parameters of particular interest are range and frequency. In order to demonstrate key sensitivities, stratified environmental models are used. The models include one or more sediment layers. Variability in the environment is assumed to arise from small random fluctuations in sound speed throughout the layer and at layer interfaces. Formulas based on a perturbation treatment of the Helmholtz equation are used.