Use of Signal and Ambient Noise Coherence to Optimize Sonar System Performance

Acoustic signal transmissions in littoral regions can have as much as 15 to 20 dB variability due to spatial and temporal effects [1]. Recent studies have shown that the ambient noise levels in the littoral also exhibit high variability that may be correlated to the littoral environment. Since both signal and noise variability have a direct impact on sonar system performance, an initial goal of this research is to relate the fluctuations in signal and noise, and their correlations to the relevant oceanographic features such as internal solitary waves and/or tides, shelf-break fronts, internal surface ducting, etc. An additional goal of is to develop simple rules-of-thumb to provide the sonar operator with the ability to exploit the oceanographic features (that lead to changes in sonar system signal and noise levels) and thereby optimize the overall system performance.