Dear colleagues I'm happy to share the recent publication of two papers in Journal of the Acoustical Society of America.
The first paper is a comment to a recently published review of TTS-onset thresholds in seals and porpoises. In our comment, we describe why we do not find support for the conclusions reached in the review if all available literature on TTS in harbour seals and harbour porpoises is considered. The paper is not open access, so email me for reprint. The second paper is a review of studies of behavioural reactions of porpoises to underwater noise, in particular from pile driving, and provides support for the audiogram-weighted sound pressure level (rms over 125 ms) as a robust predictor for response. Link to the open access paper provided below. Best regards Jakob Tougaard Comment on “Similar susceptibility to temporary hearing threshold shifts despite different audiograms in harbor porpoises and harbor seals” [J. Acoust. Soc. Am. 155, 396–404 (2024)] (L) https://doi.org/10.1121/10.0035452 Gransier and Kastelein [J. Acoust. Soc. Am. 155, 396–404 (2024)] present a review of selected studies on temporary threshold shift (TTS) in seals and porpoises. In contrast to the conclusion made in the paper, the results presented are fully consistent with the current understanding that sound exposure level is the best overall predictor of TTSs in marine mammals. If all available TTS studies on seals and porpoises exposed to narrowband noise are included, there is support neither for the conclusion that seals and porpoises are equally susceptible to TTSs nor for their claim that audiograms are poor predictors of the frequency dependence of TTS susceptibility. Behavioral reactions of harbor porpoises to impact pile driving noise are predicted by the auditory frequency weighted sound pressure level https://doi.org/10.1121/10.0035916 Offshore impact pile driving is a major source of high level underwater noise that can disturb marine mammal behavior tens of kilometers away. Projects involving pile driving are therefore subject to environmental impact assessments, which include modelling of the spatial extent of the behavioral disturbance. Reliable predictions about behavioral reaction distances require robust estimates of the minimum received levels of noise above which animals are likely to respond. Studies of reactions of harbor porpoises to pile driving noise in the wild and playback in captivity were identified, and reaction thresholds were extracted. Thresholds were weighted with the auditory frequency weighting function for VHF-cetaceans, the functional hearing group to which porpoises belong. The thresholds derived from playback studies to animals in captivity could be frequency weighted directly, whereas thresholds from exposure to noise from actual pile driving activities were weighted via a range-dependent weighting factor. Seven studies of porpoise reactions provided a first estimate of a behavioral reaction threshold as a VHF-weighted received level (Lp,125 ms,VHF) in the range 95–115 dB re 1 μPa. ************************************************************************* Jakob Tougaard, Ph.D. Professor in Marine Conservation Ecology Department of Ecoscience, section for Marine Mammal Research Aarhus University Building 1131 C.F. Møller’s Allé 3 DK-8000 Aarhus Denmark Phone: +45 4098 4585 E-mail: j...@ecos.au.dk<mailto:j...@ecos.au.dk> CVR/VAT: 31119103 EAN: 5798000419988
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