| Summary: | To protect marine mammals from potential negative impacts of high-power sound from tactical sonar, the use of passive acoustic monitoring prior and during sonar exercises is a possible non-intrusive solution for the monitoring requirements for naval forces. Particularly deep-diving beaked whales seem sensitive to sound from tactical mid-frequency sonar. Beaked whales themselves use sound of frequencies well above 20 kHz, which does not overlap with the frequency range of onboard tactical sonar systems. Therefore at TNO a dedicated passive towed hydrophone array system for marine mammal detection was developed. It consists of a an acoustic section up to 12 kHz that allows for beamforming, a high frequency section at 48 kHz and a new ultra high frequency section up to 150 kHz to which correlation techniques can be applied. The latter is an essential upgrade to enable detection and localization of beaked whales and porpoises. Real-time signal processing and monitoring is implemented on standard PCs. The processing consists of a mature transient detection system and prototypes of classification and localization functions. The software has been tested in several sea-trials and was recently applied in two Controlled Exposure Experiments. In these experiments several species were tracked, tagged and exposed to controlled levels of sonar sound.
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