Automatic Detection of Beaked Whales from Acoustic Seagliders

Abstract

Abstract : The U.S. Navy s use of tactical mid-frequency active sonar has been linked to marine mammal strandings and fatalities (NMFS 2001). These events have generated legal challenges to the Navy s peacetime use of mid-frequency sonar, and have limited the Navy s at-sea anti-submarine warfare training time. Beaked whales may be particularly sensitive to mid-frequency sonar. A mobile, persistent surveillance system that could detect, classify and localize beaked whales will help resolve the conflict between the Navy s need for realistic training of mid-frequency sonar operators and the Navy s desire to protect marine mammal populations worldwide. Underwater gliders equipped with appropriate acoustic sensors, processing, and detection systems passive acoustic monitoring (PAM) gliders may offer a partial solution to the problem. The acoustically-equipped Seaglide(trademark) from the Applied Physics Laboratory of the University of Washington (APL-UW) is one such platform. A Seaglider can travel about 20 km/day through the water for a period of weeks to months, dive from the surface to 1000 m and back in a few hours, and use two-way satellite (Iridium) telemetry for data and command transfer. This makes it potentially highly useful for the long-term goal of this project, mitigating impacts of Navy operations on marine mammals. The objective of this effort is to develop techniques for detection and classification of odontocetes echolocation clicks and especially beaked whale sounds for the PAM Seaglider. Because any methods developed must run in the operational environment of the Seaglider, they must have a low average computational cost because of the limited processing power and battery life of the Seaglider. The performance of the detection and classification system will be evaluated on several field trials.