Temporal effects of sound on the odontocete auditory system : An electrophysiological analysis

• Main Author: Mooney, T. Aran
• Format: Thesis
• Language: English
• Published: 2008
• Subjects: toothed whales
• Online Access: http://hdl.handle.net/10125/20939

Thesis (Ph.D.)--University of Hawaii at Manoa, 2008. It can be concluded that sounds of varying temporal characteristics are processed in a variety of ways. While there are similarities between odontocete species auditory systems, there are also divergent characteristics. The model of predicting threshold shift presented here was compared to both terrestrial mammal and marine mammal data to ensure robustness of data. Such auditory generalizations should be similarly carefully weighed when applied, especially regarding the many species for which little is known. Sound is likely the primary sensory modality for odontocete cetaceans (toothed whales and dolphins). As is typical of mammals, acoustic temporal patterns are important for odontocetes to detect, identify, and classify sound sources. Over-exposure to certain sounds may also affect odontocete hearing capabilities. This dissertation explores the auditory capabilities of odontocetes in respect to broadband acoustic signals of various temporal characteristics. The specific goals of the work included: (i) investigate the temporal resolution of several species of odontocetes, (ii) examine the noise exposure intensities and durations required to induce temporary hearing threshold shifts, and (iii) calculate a model of predicting threshold shift occurrence and evaluate its fit to the equal energy hypothesis of noise exposure. The results demonstrate that dolphin auditory temporal resolution is quite rapid relative to terrestrial mammals and likely capable of following echolocation clicks and echoes at very close ranges, when inter-click-intervals are very short. The odontocete temporal processing capability is similar in bandwidth across multiple species thus indicates that this trait is conserved and has likely been selected for by the need to process underwater sound and for echolocation. How odontocetes receive sound seems to differ between species and is likely dependent on the morphology of the head and acoustic fats used to gather incoming sound. ...