Temporary threshold shifts and recovery following noise exposure in the Atlantic bottlenosed dolphin (Tursiops truncatus)

Behaviorally determined hearing thresholds for a 7.5-kHz tone for an Atlantic bottlenosed dolphin (Tursiops truncatus) were obtained following exposure to fatiguing low-frequency octave band noise. The fatiguing stimulus ranged from 4 to 11 kHz and was gradually increased in intensity to 179 dB re 1 microPa and in duration to 55 min. Exposures occurred no more frequently than once per week. Measured temporary threshold shifts averaged 11 dB. Threshold determination took at least 20 min. Recovery was examined 360, 180, 90, and 45 min following exposure and was essentially complete within 45 min.