title: Cetacean noise criteria revisited in the light of proposed exposure limits for harbour porpoises.
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.
authors.affiliation: Aarhus University, Department of Bioscience, Frederiksborgvej 399, DK-4000 Roskilde, Denmark. Electronic address: jat@bios.au.dk.
authors.forename: Jakob
authors.initials: J
authors.lastname: Tougaard
authors.affiliation: Aarhus University, Department of Bioscience, Frederiksborgvej 399, DK-4000 Roskilde, Denmark; Department of Environmental Science and Policy, George Mason University, 4400 University Drive, Fairfax, VA 22030, USA.
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Wright
authors.affiliation: Aarhus University, Department of Bioscience, DK-8000 Aarhus C, Denmark; Murdoch University Cetacean Research Unit, Murdoch University, WA, Australia.
authors.forename: Peter T
authors.initials: PT
authors.lastname: Madsen
mesh_terms: D000161:Acoustic Stimulation; D000818:Animals; D050681:Bottle-Nosed Dolphin / Q000502:physiology*; D004781:Environmental Exposure / Q000331:legislation & jurisprudence*; D008027:Light; D009622:Noise; D050741:Phocoena / Q000502:physiology*; D019576:Porpoises / Q000502:physiology*; D013016:Sound; D013018:Sound Spectrography; D014481:United States
keywords: Behavioural response; Frequency weighting; Hearing; Impact assessment; Temporary threshold shift; Underwater noise