Ranging bowhead whale calls in a shallow-water dispersive waveguide

Area of Science:

• Acoustics
• Marine Biology
• Signal Processing

Background:

• Accurate localization of marine mammal vocalizations is crucial for ecological studies.
• Underwater sound propagation in waveguides presents unique challenges for acoustic ranging.
• Previous methods for bowhead whale call localization have limitations.

Purpose of the Study:

• To evaluate the performance of Conventional Mode Filtering (CMF) and Synthetic Time Reversal (STR) using a vertical array for bowhead whale call ranging.
• To compare these vertical array methods with a seafloor triangulation technique using Directional Autonomous Seafloor Acoustics Recorders (DASARs).
• To assess the effectiveness of different acoustic array configurations for underwater acoustic source localization.

Main Methods:

• Simulations and analysis of acoustic data collected near Kaktovik, Alaska in 2010.
• Deployment of a 12-element vertical array and a distributed array of seven DASARs.
• Comparison of ranging estimates from CMF, STR, and DASAR triangulation for 19 bowhead whale calls.

Main Results:

• Ranging estimates from CMF and STR were generally within ±10% of DASAR triangulation results.
• Synthetic Time Reversal (STR) demonstrated slightly better agreement with DASAR results compared to CMF.
• The vertical array proved capable of ranging whale calls at greater distances and with higher precision than the tested DASAR array, especially for calls located beyond the DASAR array's boundaries.

Conclusions:

• Both CMF and STR are effective methods for estimating bowhead whale call ranges in shallow water waveguides.
• Vertical arrays offer advantages in range and precision over distributed seafloor arrays for certain source locations.
• STR shows promise as a robust technique for acoustic source localization in complex underwater environments.