Underwater surveillance in a harbor is typically performed using active sonar systems. The performance of an active sonar can drastically change due to rapid variations in the sound propagation. This paper presents a method for detecting divers with open circuit breathing systems using passive acoustics. The authors have previously reported on a method for passive acoustic diver detection that employs two hydrophones. The proposed method uses a single hydrophone, resulting in a simpler and cheaper system. The method works by whitening the background noise and mitigating the influence of short-duration transients and rapid variations in the background noise. Results presented here show that the proposed algorithm performs better than the previous dual hydrophone method. Compared to the dual hydrophone method applied to the same frequency band, the proposed method achieves greater detection ranges at significantly lower false alarm rates. Pre-whitening permits us to use a wider analysis frequency band, resulting in further improvements to the detection range.

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