Temporary threshold shift in bottlenose dolphins (Tursiops truncatus) exposed to mid-frequency tones

• Published in: The Journal of the Acoustical Society of America Vol. 118; no. 4; p. 2696
• Main Authors: Finneran, James J, Carder, Donald A, Schlundt, Carolyn E, Ridgway, Sam H
• Format: Journal Article
• Language: English
• Published: United States 01.10.2005
• Subjects: Acoustic Stimulation; Animals; Audiometry, Pure-Tone - veterinary; Auditory Fatigue - physiology; Auditory Threshold - physiology; Bottle-Nosed Dolphin - physiology; Male; Noise - adverse effects
• ISSN: 0001-4966
• DOI: 10.1121/1.2032087

A behavioral response paradigm was used to measure hearing thresholds in bottlenose dolphins before and after exposure to 3 kHz tones with sound exposure levels (SELs) from 100 to 203 dB re 1 microPa2 s. Experiments were conducted in a relatively quiet pool with ambient noise levels below 55 dB re 1 microPa2/Hz at frequencies above 1 kHz. Experiments 1 and 2 featured 1-s exposures with hearing tested at 4.5 and 3 kHz, respectively. Experiment 3 featured 2-, 4-, and 8-s exposures with hearing tested at 4.5 kHz. For experiment 2, there were no significant differences between control and exposure sessions. For experiments 1 and 3, exposures with SEL=197 dB re 1 microPa2 s and SEL > or = 195 dB re 1 microPa2 s, respectively, resulted in significantly higher TTS4 than control sessions. For experiment 3 at SEL= 195 dB re 1 microPa2 s, the mean TTS4 was 2.8 dB. These data are consistent with prior studies of TTS in dolphins exposed to pure tones and octave band noise and suggest that a SEL of 195 dB re 1 microPa2 s is a reasonable threshold for the onset of TTS in dolphins and white whales exposed to midfrequency tones.