[MARMAM] New Publication: Airgun Pulses in Shallow Water with Implications for Effects on Small Marine Mammals

Line Hermannsen line.hermannsen at gmail.com
Thu Aug 6 07:00:40 PDT 2015

Dear MARMAMers,

We are pleased to announce the publication of the following paper in PLOS

*"Characteristics and Propagation of Airgun Pulses in Shallow Water with
Implications for Effects on Small Marine Mammals"*
Hermannsen, L., Tougaard, J., Beedholm, K., Nabe-Nielsen, J. and Madsen P.T.
PLOS ONE, July 27, 2015.URL:
DOI: 10.1371/journal.pone.0133436 AbstractAirguns used in seismic surveys
are among the most prevalent and powerful anthropogenic noise sources in
marine habitats. They are designed to produce most energy below 100 Hz, but
the pulses have also been reported to contain medium-to-high frequency
components with the potential to affect small marine mammals, which have
their best hearing sensitivity at higher frequencies. In shallow water
environments, inhabited by many of such species, the impact of airgun noise
may be particularly challenging to assess due to complex propagation
conditions. To alleviate the current lack of knowledge on the
characteristics and propagation of airgun pulses in shallow water with
implications for effects on small marine mammals, we recorded pulses from a
single airgun with three operating volumes (10 in3, 25 in3 and 40 in3) at
six ranges (6, 120, 200, 400, 800 and 1300 m) in a uniform shallow water
habitat using two calibrated Reson 4014 hydrophones and four DSG-Ocean
acoustic data recorders. We show that airgun pulses in this shallow habitat
propagated out to 1300 meters in a way that can be approximated by a
18log(r) geometric transmission loss model, but with a high pass filter
effect from the shallow water depth. Source levels were back-calculated to
192 dB re µPa2s (sound exposure level) and 200 dB re 1 µPa dB Leq-fast (rms
over 125 ms duration), and the pulses contained substantial energy up to 10
kHz, even at the furthest recording station at 1300 meters. We conclude
that the risk of causing hearing damage when using single airguns in
shallow waters is small for both pinnipeds and porpoises. However, there is
substantial potential for significant behavioral responses out to several
km from the airgun, well beyond the commonly used shut-down zone of 500

For those interested in reading more, this paper and other interesting
papers from our Marine Bioacoustics Lab can be downloaded from:
www.marinebioacoustics.com/pub.php Best regards,Line Hermannsen

*Line Hermannsen*
*Department of Bioscience*
*Aarhus University*
*mail: line.hermannsen at gmail.com <line.hermannsen at gmail.com> or
lihe at bios.au.dk <lihe at bios.au.dk>*
*telephone: +45 22 82 56 61 <%2B45%2022%2082%2056%2061>*
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