Fortuitous underwater acoustic measurements of baleen whale vocalizations by large aperture arrays

Over the past several years, the Marine Physical Laboratory has designed, built, and deployed innovative, large‐aperture sensor systems in order to measure the low‐frequency properties of the ocean acoustic field. In many of these experiments, baleen whale vocalizations have been a significant feature of the infrasonic sound field. For example, finback whale (Balaenoptera physalus) sounds have been recorded by a 120‐element, 900‐m, vertical line array of hydrophones. Finback whale sounds were also recorded by a 12‐element, 165‐m, vertical array of ‘‘TRIFAR’’ elements (i.e., each element records simultaneously the three components of acoustic particle velocity and pressure). In addition, blue whale (Balaenoptera musculus) signals were the overwhelming feature of a data set recorded by some neutrally buoyant, freely drifting, acoustic particle motion/acoustic pressure sensors. Finally, new‐design ocean bottom seismometers (OBS) have recorded both finback and blue whale signals. Where possible, these measurements are used to estimate both the position and the actual time signature of the source by removing the effects of multipath arrivals.