Whales in Space: Experiencing Aquatic Animals in Their Natural Place with the Hydroambiphone
Recording the undersea three-dimensional bioacoustic sound field in real-time promises major benefits to marine behavior studies. We describe a novel hydrophone array--the hydroambiphone (HAP)--that adapts ambisonic spatial-audio theory to sound propagation in ocean waters to realize many of these benefits through spatial localization and acoustic immersion. Deploying it to monitor the humpback whales (Megaptera novaeangliae) of southeast Alaska demonstrates that HAP recording provides a qualitatively-improved experience of their undersea behaviors; revealing, for example, new aspects of social coordination during bubble-net feeding. On the practical side, spatialized hydrophone recording greatly reduces post-field analytical and computational challenges--such as the "cocktail party problem" of distinguishing single sources in a complicated and crowded auditory environment--that are common to field recordings. On the scientific side, comparing the HAPs capabilities to single-hydrophone and nonspatialized recordings yields new insights into the spatial information that allows animals to thrive in complex acoustic environments. Spatialized bioacoustics markedly improves access to the humpbacks undersea acoustic environment and expands our appreciation of their rich vocal lives.