Site-specific passive sonar performance prediction

A measurement-based plan and methodology are discussed for predicting a passive sonar performance dB-budget at a specific candidate site for which only single omnidirectional hydrophone data is available. Analysis of 24/7 calibrated hydrophone data supports detailed performance forecasting for a costly, large scale acoustic observatory. The candidate site selected for consideration is in a bottom-limited littoral contiguous to a commercial port with a very high level of surface ship traffic. The acoustic data allows the statistical characterization of horizontal coherence distance, acoustic ambient noise floor and peak absolute acoustic sound pressure for so-called high level events (HLEs) due to the passage of surface ships. Histogram analysis of the absolute level of HLEs is used in conjunction with conventional (time delay-and-sum) beamforming (CBF) sidelobe levels to predict optimum-adaptive beamforming (ABF) array gain improvement (AGI). For the specific site considered, time intervals of AGI for ABF relative to CBF greater than 20 dB are predicted.