Non-Plane-Wave Noise Source Localization in Very Shallow Water

Spatial processing for Navy arrays has been designed in nearly all cases based on the a horizontally propagating plane wave model, the underlying assumption being that energy arrives from far field targets as a superposition of free field traveling waves at frequencies determined by the target signature. It is well known that acoustic propagation is much more complex than the simple model due to boundary interactions (as evidenced by multi-path), sound velocity variability, and other more complicated effects. These effects are most prominent in shallow water and at low frequencies where surface and bottom interactions are prevalent. The Phase I research on this topic has derived an effective method of predicting the arrival structure of complicated multipath and applying a novel broadband statistical method for recombining the diverse acoustic paths. The Phase I effort derived the theoretical basis for the method and demonstrated its feasibility. The Phase II research will investigate the robustness of the method to environmental uncertainty, apply it to more complicated environments, and extend it to narrowband processing for target classification.