NPAL Acoustic Coherence And Broadband Full Field Processing

Noise fields in most sonar models are characterized nonparametrically wherein a noise coherence matrix for the array of sensors is estimated across frequency. Arrays are now becoming so large that is difficult to estimate this matrix reliably because of the nonstationarity. In many environments shipping is a dominant part of the noise field and it does not take much source receiver motion to lead to variablity and nonstationarity in the noise field. The variability induced by motion is often much larger than that induced by natural processes such as surface or internal waves. An approach to mitigating this problem is to substitute a priori models for some components of the noise field such as the strong, directional ones. A model must incorporate spatial coherence to be useful for sonars withlarge arrays. My objective is to determine robust models for directional noise sources which include the effects of source motion as well as natural ocean processes and to evaluate their utility for sonar array processing algorithms.