A large-aperture low-cost hydrophone array for tracking whales from small boats

Area of Science:

• Marine bioacoustics
• Cetacean behavioral ecology
• Passive acoustic monitoring

Background:

• Tracking diving marine mammals in three dimensions is challenging.
• Small vessel deployment offers logistical advantages for acoustic monitoring.

Purpose of the Study:

• To present a passive sonar array for 3D sperm whale tracking from a small vessel.
• To describe the system's advantages and limitations.
• To analyze the system's performance in real-world conditions.

Main Methods:

• A four-buoy passive sonar array with hydrophones, recorders, and GPS, plus a vertical stereo hydrophone array.
• GPS synchronization of recordings.
• Hyperbolic localization methods and isodiachronic sequential bound estimation for 3D localization.
• Post-processing of recordings for diving profile analysis.

Main Results:

• Successful deployment of the passive sonar array from a 6m boat.
• Obtained 3D localization data for vocalizing sperm whales.
• Demonstrated the system's capability to generate diving profiles.
• Compared localization accuracy using different methods.

Conclusions:

• The described passive sonar array is a viable tool for 3D tracking of sperm whales from small vessels.
• The system provides valuable data for understanding sperm whale diving behavior.
• Further analysis can refine localization accuracy and expand applications.