Background and objectives
Knowledge about the basic hearing abilities of marine mammals is fundamental for all further auditory and bio-acoustic research and also for the evaluation and mitigation of possible impacts of anthropogenic noise. Audible frequency ranges and corresponding hearing thresholds are the most characteri...
| Main Authors: | , , |
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| Format: | Text |
| Language: | English |
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| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.72.694 http://www.awi.de/acoustics/Publications/pubs/Cruise_Report_ANT-LAND-05-06_ABR.pdf |
| Summary: | Knowledge about the basic hearing abilities of marine mammals is fundamental for all further auditory and bio-acoustic research and also for the evaluation and mitigation of possible impacts of anthropogenic noise. Audible frequency ranges and corresponding hearing thresholds are the most characteristic properties of the auditory system for any species. They are typically displayed in the form of an audiogram as the function of minimal audible sound level in respect to frequency. For about 90 % of marine mammal species including all Antarctic seals, audiograms have not been measured yet. Audiograms can either be obtained by training subjects to react in a deterministic manner to any sound stimulus within their hearing range, or by using neurophysiologic techniques to measure the brain’s bioelectric responses to a given acoustic input. Behavioural audiograms, which are the common method to test human hearing abilities, are impossible to obtain from wild animals. Hence we measured auditory evoked potentials (AEP), especially the auditory brainstem responses (ABR) of immobilised Weddell seals by electro-encephalogram (EEG) electrodes. This non invasive method is frequently used in neonatology to test for hearing disabilities of newborn humans. It is also common for the investigation of hearing in dolphins and whales (Supin, 1993) but has only recently been adopted to harbour seals, where amplitudes of the evoked responses are much smaller and thus harder to detect (Wolski |
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