Temporary threshold shift in bottlenose dolphins (Tursiops truncatus) exposed to mid-frequency tones.
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.
Finneran
James J
JJ
U.S. Navy Marine Mammal Program, Space and Naval Warfare Systems Center, San Diego, Code 2351, San Diego, California 92152, USA. james.finneran@navy.mil
Carder
Donald A
DA
Schlundt
Carolyn E
CE
Ridgway
Sam H
SH
D000161:Acoustic Stimulation; D000818:Animals; D001301:Audiometry, Pure-Tone / Q000662:veterinary; D001305:Auditory Fatigue / Q000502:physiology*; D001309:Auditory Threshold / Q000502:physiology; D050681:Bottle-Nosed Dolphin / Q000502:physiology*; D008297:Male; D009622:Noise / Q000009:adverse effects*