Resolving acoustic azimuth using an accelerometer-based underwater acoustic vector sensor

Abstract

The performance of a single commercial accelerometer-based underwater acoustic vector sensor (AVS) in resolving acoustic azimuth was evaluated. The method involves calculating the active intensity of an acoustic signal to determine the dominant directionality of an acoustic pressure field as a function of time and frequency. While this method efficiently displays azimuth bearings for specific frequencies, there are very few assessments of its performance in resolving all possible bearings using a single AVS. Field experiments were conducted with an AVS placed on the sea bottom and an active source suspended from a research vessel. A 600 Hz signal was transmitted from 16 positions covering a 360° azimuth to the AVS. During the transmissions, the vessel maintained its position and heading by using a dynamic positioning system. The acoustic azimuths were compared with the transmission bearings obtained via Global Positioning System. This study demonstrates that a commercial AVS system can effectively resolve acoustic bearings across a full 360° azimuth at high signal-to-noise ratios using the active intensity method. Our results support the use of AVS systems in research on sound directionality, including bioacoustics studies on how marine organisms respond to natural underwater sound and anthropogenic noise.