[MARMAM] New publication: Lombard effect in humpback whales

Regina Guazzo rguazzo at ucsd.edu
Tue Aug 4 12:16:17 PDT 2020


Dear Colleagues,

I hope you are all well.  My co-authors and I are excited to announce the
following open-access publication:

Guazzo RA, Helble TA, Alongi GC, Durbach IN, Martin CR, Martin SW,
Henderson EE (2020). The Lombard effect in singing humpback whales: Source
levels increase as ambient ocean noise levels increase. J. Acoust.Soc. Am.
148(2): 542-555.

DOI: https://doi.org/10.1121/10.0001669

Abstract:
Many animals increase the intensity of their vocalizations in increased
noise. This response is known as the Lombard effect. While some previous
studies about cetaceans report a 1 dB increase in the source level (SL) for
every dB increase in the background noise level (NL), more recent data have
not supported this compensation ability. The purpose of this study was to
calculate the SLs of humpback whale song units recorded off Hawaii and test
for a relationship between these SLs and background NLs. Opportunistic
recordings during 2012-2017 were used to detect and track 524 humpback
whale encounters comprised of 83,974 units on the U.S. Navy’s Pacific
Missile Range Facility hydrophones. Received levels were added to their
estimated transmission losses to calculate SLs. Humpback whale song units
had a median SL of 173 dB re 1 uPa at 1 m, and SLs increased by 0.53 dB/1
dB increase in background NLs. These changes occurred in real time on
hourly and daily time scales. Increases in ambient noise could reduce male
humpback whale communication space in the important breeding area off
Hawaii.  Since these vocalization changes may be dependent on location or
behavioral state, more work is needed at other locations and with other
species.

Please email me (regina.guazzo at spawar.navy.mil) if you have any questions
about this work.

All my best,

Regina

Regina A. Guazzo, PhD
Whale Acoustics Reconnaissance Program (WARP)
Environmental Readiness Branch
Naval Information Warfare Center Pacific
(c) 908.507.1421
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