Passive acoustic detection and localization of Mesoplodon densirostris (Blainville's beaked whale) vocalizations using distributed bottom-mounted hydrophones in conjunction with a Digital Tag (DTAG) recording

Abstract

Click data from a tagged Mesoplodon densirostris was compared with broadband acoustic recordings from an 82 hydrophone wide-baseline array located in the Tongue of the Ocean, Bahamas. Two detectors, a Fast Fourier Transform (FFT) based detector and matched filter, were evaluated in white noise and with the acoustic recordings from the array for performance detecting M. densirostris clicks. The matched filter performed the best, allowing 92% of the tagged animal's clicks to be detected on at least one hydrophone. Time Difference of Arrivals (TDOAs) between the DTag and the surrounding hydrophones were computed. These TDOAs were used to compute a three-dimensional hyperbolic localization track of the tagged animal. A maximum detection range of 6500 m from the tagged animal to the recording hydrophone was observed. Offset aspect angles were determined from the DTag heading information and the bearing to the receiving hydrophone. Clicks within ±30 degrees were detected at the farthest ranges, while clicks were detected at all off-set angles at closer ranges.