Noise Impacts on Pinniped Hearing
Final rept. 23 Feb 2004-22 Jan 2006
CALIFORNIA UNIV SANTA CRUZ INST OF MARINE SCIENCES
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The National Research Council, in a series of recent reports on marine mammals and anthropogenic noise, has identified the need to develop and test predictive models of acoustic conditions that would harm marine mammals. The primary aim of the current study was to assess the effects of intense, octave bands of noise on auditory sensitivity in three pinniped species. Specifically, temporary threshold shifts ranging up to 30 dB were induced in trained subjects in order to evaluate the relative effects of noise level and duration. Results showed that TTS onset occurred when noise levels exceeded hearing threshold by 80 dB for 12 minutes or more, irrespective of whether noise exposure occurred in air or under water. This corresponds to exposure levels of about 150-160 dB SEL in air and 183-207 dB SEL under water. Growth of TTS followed a modified exponential model rather than a simple equal energy trading model. Complementary field studies at harbor seal and northern elephant seal breeding areas characterized ambient noise environments and examined whether call features varied as a function of background noise levels.
- Anatomy and Physiology
- Biological Oceanography