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Title: Evoked-potential audiogram of an Indo-Pacific humpback dolphin (Sousa chinensis)
Authors: Li, S. 
Wang, D.
Wang, K.
Taylor, E.A.
Cros, E. 
Shi, W.
Wang, Z.
Fang, L.
Chen, Y.
Kong, F.
Keywords: AEP response
Hearing sensitivity
Marine mammal
Issue Date: Sep-2012
Citation: Li, S., Wang, D., Wang, K., Taylor, E.A., Cros, E., Shi, W., Wang, Z., Fang, L., Chen, Y., Kong, F. (2012-09). Evoked-potential audiogram of an Indo-Pacific humpback dolphin (Sousa chinensis). Journal of Experimental Biology 215 (17) : 3055-3063. ScholarBank@NUS Repository.
Abstract: An evoked-potential audiogram was measured for an Indo-Pacific humpback dolphin (Sousa chinensis) living in the dolphinarium of Nanning Zoo, China. Rhythmic 20 ms pip trains composed of cosine-enveloped 0.25 ms tone pips at a pip rate of 1 kHz were presented as sound stimuli. The dolphin was trained to remain still at the water surface and to wear soft latex suction-cup EEG electrodes used to measure the animal's envelope-following evoked potentials to the sound stimuli. Responses to 1000 rhythmic 20 ms pip trains for each amplitude/frequency combination were averaged and analysed using a fast Fourier transform to obtain an evoked auditory response. The hearing threshold was defined as the zero crossing point of the response input-output function using linear regression. Fourteen frequencies ranging from 5.6 to 152 kHz were studied. The results showed that most of the thresholds were lower than 90dBre. 1 μPa (r.m.s.), covering a frequency range from 11.2 to 128 kHz, and the lowest threshold of 47dB was measured at 45 kHz. The audiogram, which is a function of hearing threshold versus stimulus carrier frequency, presented a U-shape with a region of high hearing sensitivity (within 20dB of the lowest threshold) between approximately 20 and 120 kHz. At frequencies lower than this high-sensitivity region, thresholds increased at a rate of approximately 11 dB octave-1 up to 93dB at 5.6kHz. The thresholds at high frequencies above 108kHz increased steeply at a rate of 130dBoctave-1 up to 127dB at 152 kHz. © 2012. Published by The Company of Biologists Ltd.
Source Title: Journal of Experimental Biology
ISSN: 00220949
DOI: 10.1242/jeb.070904
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