NPAL Acoustic Coherence and Broadband Full Field Processing
Abstract
LONG TERM GOALS. The long term goals are i) to measure and model the horizontal and vertical coherence of the array data from the North Pacific Acoustic Laboratory (NPAL) and ii) to specify stochastic models for representing these data foe inclusion in broadband passive sonar processing algorithms. OBJECTIVES. Noise fields in most sonar models are characterized nonparametrically wherein the noise coherence matrix for an array of sensors is estimated across frequency with no constraints imposed upon it by the propagation physics. Arrays are now becoming so large that is difficult to estimate this coherence matrix reliably because of the constraints of nonstationarity. [1] In many environments shipping is a dominant component of the noise field and it does not take much source-receiver motion to introduce variability and nonstationarity in the noise field. The motion induced variability is much larger than that caused by natural processes such as surface or internal waves. The ambient field is simply not stationary long enough to be well characterized nonparametrically. An approach to mitigating this problem is to substitute a priori models for some components of the noise field such as the ones generated by strong, directional sources from shipping. Moreover, the effects of motion are induced across the band which can provide additional constraints if one can incorporate them in a robust way. The fundamental problem is the stochastic nature of the propagation introduces variablity, so signals from a directional source cannot be simply characterized by running a deterministic propagation code. My objective is determine robust models for directional sources using using data from the NPAL arrays and to evaluate their utility for sonar array processing algorithms.
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 30, 1999
- Accession Number
- ADA630249
Entities
People
- Arthur Bernard Baggeroer
Organizations
- Massachusetts Institute of Technology