[MARMAM] new publication on killer whale calls and noise

Marla Holt Marla.Holt at noaa.gov
Wed Nov 16 14:22:00 PST 2011

We are pleased to announce that the following article has just been 

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: 

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 

© 2011 /Acoustical Society of America/

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

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