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Passive Acoustic Methods for Tracking Marine Mammals Using Widely-Spaced Bottom-Mounted Hydrophones

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Annual rept.

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The long-term goal of this project is to improve passive acoustic methods for tracking marine mammals, with the primary effort dedicated to methods that use bottom-mounted hydrophones. When possible, tracking results are used to study marine mammal behavior and bioacoustics. The specific objective of the project is to develop and implement methods to deal with two specific challenges associated with tracking marine mammals using widely-spaced bottom-mounted hydrophone arrays 1 multiple animals whose calls cannot be easily separated or associated, and 2 insufficient receiver coverage, in which case standard time-of-arrival TOA tracking methods fail. The project uses existing datasets to develop and apply the tracking methods. The main effort is directed toward data collected at Navy Ranges. The main species of interest are sperm whales, beaked whales, minke whales, and humpback whales. Most methods will be generalizable to other species. Although the two main tracking challenges addressed by this project insufficient receiver coverage and multiple animals are not exclusive of one another, initial efforts focus on isolating the problems and solving them separately. As the separate challenges are met, efforts will progress to the joint problem. Model-based tracking methods are used since they can account for depth-dependent sound speed profiles particularly important as refraction becomes significant at long distances, such as on Navy ranges and since they can accurately model and make use of multi-path arrivals. Methods are implemented using a Bayesian framework to incorporate available a priori information, get error estimates on position, and improve performance in uncertain and fluctuating environments. In this framework, a three-dimensional grid is created and the likelihood of an animal present is calculated for each grid point and time.

Subject Categories:

  • Biology
  • Acoustic Detection and Detectors
  • Acoustics

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