UC San Diego

The oceans contain a cacophony of sounds from biological, geological, meteorological, and anthropogenic sources. As computational power and data storage capabilities have increased, long-term passive acoustic recordings have been increasingly employed to study the oceans. Multiple hydrophones can be deployed in a site or region to gain more information on the spatial properties of acoustic soundscapes. In this thesis, we use hydrophone arrays to track vocalizing animals and anthropogenic sound sources, and by so doing gain valuable insights into ocean environments.

Chapter 1 introduces Where's Whaledo: software toolkit and workflow for efficiently and reliably localizing and tracking groups of vocalizing animals. Methods were developed to identify and remove false detections in small-aperture direction of arrival estimates, associate detections across widely-spaced instruments using click trains, estimate source locations, and calculate confidence intervals.

Chapter 2 employs Where's Whaledo on Ziphius cavirostris (Zc) in the Tanner Basin, demonstrating the toolkit's capabilities by reconstructing the tracks of 143 dives. The localized animals demonstrated a preference for the steeper bathymetry at the study site, as well as a possible preference for swimming in groups of two or more animals. 12 of these tracks were used to estimate the beam pattern of a Zc echolocation click.

Chapter 3 demonstrates the challenges and complexities of long-range propagation by examining recordings of five vessels performing a coordinated seismic survey using high-intensity signals from airgun arrays. Using several identifiable patterns in the acoustic data, each arrival in a 110-minute period was associated with its source vessel so changes in dispersion patterns could be observed over time. Both ray trace and parabolic equation models were used to simulate dispersion patterns. Potential causes of differences between the modeled signals and the observed signals are discussed, and recommendations are made for future analyses.