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YIP Expansion: Ocean Basin Impact of Ambient Noise on Marine Mammal Detectability, Distribution, and Acoustic Communication

Descriptive Note:

[Technical Report, Annual Report]

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Results from the original award effort revealed that ocean sound levels have increased in the Indian Ocean, but have not uniformly increased across the globe. Ambient sound levels decreased over the past decade in the Equatorial Pacific and South Atlantic Oceans. This expanded research effort extends the trend analyses of decadal ocean sound levels completed under the original award to an analysis of trends and shifts in characteristics of specific sources contributing to the soundscape over time. The primary sources of interest are baleen whales, as it is critical to identify any shift in vocalization characteristics over time to ensure optimal performance of automatic detectors used in passive acoustic monitoring, mitigation and density estimation applications. Secondary sources of interest are seismic airgun signals, shipping, and geophysical contributions from wind and ice contributions from these sources have the potential to mask biological signals targeted in monitoring and mitigation efforts and to impact animal behavior. Major goal of the proposed work is to relate observed ocean sound trends to changes in source patterns and acoustic characteristics over the past decade. 1. To assess temporal pattern, acoustic frequency, and geospatial distribution shifts of low frequency whale vocalizations over the past decade. 2. To assess temporal pattern, acoustic frequency, and geospatial distribution shifts of relevant anthropogenic and geophysical sources over the past decade. 3. To relate any observed shift in source category parameters to regional sound level trends. Identifying and quantifying the shift in source characteristics contributing to the overall soundscape is critical in monitoring and mitigation efforts. Understanding of effects of sound at the population level is vital to ultimately determining any overarching biological significance of changing ambient sound levels or source activities and extends our knowledge of individual responses.


Subject Categories:

  • Biological Oceanography
  • Physical and Dynamic Oceanography
  • Acoustics

Distribution Statement:

[A, Approved For Public Release]