PSYCHOLOGY MASTER'S THESIS ABSTRACT

Carolyn E. Schlundt
MA-Research
December 1999

The Effect of Projector Position on the Hearing Thresholds of Dolphins (Tursiops truncates) at 2, 8, and 12 kHz

    There is concern that human-generated noise in the ocean might interfere with marine mammals’ survival.  Accurate knowledge of their hearing ability is central to establishing safe noise parameters.  Most cetacean audiograms were produced using a transducer positioned in front of the animal, yet several studies suggest a frequency dependence on the location of the sound source.  This study provides the first comparison of underwater hearing thresholds in two dolphins when the project delivered test tones at 2, 8, and 12 kHz from two positions, in front and below the animal.  Results showed that 2-kHz thresholds were almost 12 dB lower when the projector was in the below position.  Thresholds at 12 kHz were 10 dB lower when the projector was in the in-front position.  The findings suggest that the low-frequency portion of cetacean audiograms might be re-evaluated to reflect the increased hearing sensitivity exhibited with a change of projector position.

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