[MARMAM] New paper on noise exposure criteria for porpoises

Jakob Tougaard jat at bios.au.dk
Sat Nov 22 00:36:31 PST 2014


I'm happy to announce that the following paper is now available as online-early from Marine Pollution Bulletin (open access).

Cetacean noise criteria revisited in the light of proposed exposure limits for harbour porpoises
by Jakob Tougaard, Andrew J. Wright and Peter T. Madsen.

Abstract
The impact of underwater noise on marine life calls for identification of exposure criteria to inform mitigation. Here we review recent experimental evidence with focus on the high-frequency cetaceans and discuss scientifically-based initial exposure criteria. A range of new TTS experiments suggest that harbour and finless porpoises are more sensitive to sound than expected from extrapolations based on results from bottlenose dolphins. Furthermore, the results from TTS experiments and field studies of behavioural reactions to noise, suggest that response thresholds and TTS critically depend on stimulus frequency. Sound exposure levels for pure tones that induce TTS are reasonably consistent at about 100 dB above the hearing threshold for pure tones and sound pressure thresholds for avoidance reactions are in the range of 40-50 dB above the hearing threshold. We propose that frequency weighting with a filter function approximating the inversed audiogram might be appropriate when assessing impact.

Highlights
*    The current acoustic exposure criteria for marine mammals are in need of revision.
*    Severity of behavioural responses does not correlate well with long term consequences for animals.
*    Review of TTS experiments on porpoises suggests that inverse audiogram weighting is appropriate.
*    Thresholds for acoustic avoidance behaviour in porpoises are also correlated with audibility.
*    Thresholds can be normalised as rms sound pressure levels averaged over 125 ms.

The text is open access and can be downloaded from this link:
doi:10.1016/j.marpolbul.2014.10.051<http://dx.doi.org/10.1016/j.marpolbul.2014.10.051>

Best regards

Jakob (jat at bios.au.dk)

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