Temporary shift in masked hearing thresholds in odontocetes after exposure to single underwater impulses from a seismic watergun.
A behavioral response paradigm was used to measure masked underwater hearing thresholds in a bottlenose dolphin (Tursiops truncatus) and a white whale (Delphinapterus leucas) before and after exposure to single underwater impulsive sounds produced from a seismic watergun. Pre- and postexposure thresholds were compared to determine if a temporary shift in masked hearing thresholds (MTTS), defined as a 6-dB or larger increase in postexposure thresholds, occurred. Hearing thresholds were measured at 0.4, 4, and 30 kHz. MTTSs of 7 and 6 dB were observed in the white whale at 0.4 and 30 kHz, respectively, approximately 2 min following exposure to single impulses with peak pressures of 160 kPa, peak-to-peak pressures of 226 dB re 1 microPa, and total energy fluxes of 186 dB re 1 microPa2 x s. Thresholds returned to within 2 dB of the preexposure value approximately 4 min after exposure. No MTTS was observed in the dolphin at the highest exposure conditions: 207 kPa peak pressure, 228 dB re 1 microPa peak-to-peak pressure, and 188 dB re 1 microPa2 x s total energy flux.
Finneran
James J
JJ
Space and Naval Warfare Systems Center, San Diego, California 92152-5000, USA.
Schlundt
Carolyn E
CE
Dear
Randall
R
Carder
Donald A
DA
Ridgway
Sam H
SH
D000161:Acoustic Stimulation; D000818:Animals; D001305:Auditory Fatigue; D001309:Auditory Threshold; D004289:Dolphins / Q000523:psychology*; D008144:Loudness Perception; D010470:Perceptual Masking; D010897:Pitch Discrimination; D013018:Sound Spectrography; D014907:Whales / Q000523:psychology*