Tracking sperm whales with a towed acoustic vector sensor

Passive acoustic towed linear arrays are increasingly used to detect marine mammal sounds during mobile anthropogenic activities. However, these arrays cannot resolve between signals arriving from the port or starboard without vessel course changes or multiple cable deployments, and their performanc...

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Bibliographic Details
Published in:The Journal of the Acoustical Society of America 2010-11, Vol.128 (5), p.2681-2694
Main Authors: Thode, Aaron, Skinner, Jeff, Scott, Pam, Roswell, Jeremy, Straley, Janice, Folkert, Kendall
Format: Article
Language:English
Subjects:
Acoustics
Acoustics - instrumentation
Animal Migration
Animals
Cetacea
Environmental Monitoring - methods
Exact sciences and technology
Fisheries
Fundamental areas of phenomenology (including applications)
Marine
Models, Theoretical
Physics
Ships
Sperm Whale
Underwater sound
Vocalization, Animal
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Summary:Passive acoustic towed linear arrays are increasingly used to detect marine mammal sounds during mobile anthropogenic activities. However, these arrays cannot resolve between signals arriving from the port or starboard without vessel course changes or multiple cable deployments, and their performance is degraded by vessel self-noise and non-acoustic mechanical vibration. In principle acoustic vector sensors can resolve these directional ambiguities, as well as flag the presence of non-acoustic contamination, provided that the vibration-sensitive sensors can be successfully integrated into compact tow modules. Here a vector sensor module attached to the end of a 800 m towed array is used to detect and localize 1813 sperm whale "clicks" off the coast of Sitka, AK. Three methods were used to identify frequency regimes relatively free of non-acoustic noise contamination, and then the active intensity (propagating energy) of the signal was computed between 4-10 kHz along three orthogonal directions, providing unambiguous bearing estimates of two sperm whales over time. These bearing estimates are consistent with those obtained via conventional methods, but the standard deviations of the vector sensor bearing estimates are twice those of the conventionally-derived bearings. The resolved ambiguities of the bearings deduced from vessel course changes match the vector sensor predictions.
ISSN:0001-4966
1520-8524
DOI:10.1121/1.3495945