Uncertainty in acoustic mine detection due to environmental variability

Abstract

Uncertainty in acoustic bottom target detection due to environmental variability for a shallow sea (30 m water depth) is investigated using the Navy’s Comprehensive Acoustic Simulation System/Gaussian Ray Bundle model for a generic Very High Frequency (VHF) forward looking sonar. The effects of imprecise bottom type and wind speed data are evaluated to determine the impact of this variability on bottom target detection. The acoustic uncertainty due to the wind variability is more sensitive to muddy sand than to and sandy silt. Maximum acoustic uncertainty due to wind variability is 9 dB for the muddy sand and 6 dB for the sandy silt. For the bottom target detection, the wind speed accuracy is extremely important. If wind speed uncertainty exceeds 7 kts, the bottom target is unlikely to be detected. The signal excess variability is small and operational benefits may be maximized with slightly better sonar. Deep transducer (depth: 25 m) demonstrates substantial signal excesses up to 23 dB compared to 7 dB for shallow transducer (depth: 5.18 m). Therefore, to increase the probability of bottom target detection utilizing the generic VHF forward looking sonar, placement of the transducer deeper in the water column is recommended.