We are pleased to announce that the following article has just been
published.
Holt, M.M., Noren, D., and Emmons, C. 2011. The effects of noise levels
and call types on the source levels of killer whale calls. Journal of
the Acoustical Society of America.130: 3100-3106.
The publication is available online at:
http://link.aip.org/link/?JAS/130/3100
Abstract:
Accurate parameter estimates relevant to the vocal behavior of marine
mammals are needed to assess potential effects of anthropogenic sound
exposure including how masking noise reduces the active space of sounds
used for communication. Information about how these animals modify their
vocal behavior in response to noise exposure is also needed for such
assessment. Prior studies have reported variations in the source levels
of killer whale sounds, and a more recent study reported that killer
whales compensate for vessel masking noise by increasing their call
amplitude. The objectives of the current study were to investigate the
source levels of a variety of call types in southern resident killer
whales while also considering background noise level as a likely factor
related to call source level variability. The source levels of 763
discrete calls along with corresponding background noise were measured
over three summer field seasons in the waters surrounding the San Juan
Islands, WA. Both noise level and call type were significant factors on
call source levels (1–40 kHz band, range of 135.0–175.7 dB_rms re 1 µPa
at 1 m). These factors should be considered in models that predict how
anthropogenic masking noise reduces vocal communication space in marine
mammals.
© 2011 /Acoustical Society of America/
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__________________________________
Marla M. Holt, Ph.D.
Research Wildlife Biologist
Marine Mammal Ecology Team
NOAA/NMFS Northwest Fisheries Science Center
2725 Montlake Blvd East
Seattle, WA 98112
www.nwfsc.noaa.gov/research/divisions/cbd/marine_mammal/marinemammal.cfm
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