Underwater temporary threshold shift in pinnipeds: effects of noise level and duration.
Behavioral psychophysical techniques were used to evaluate the residual effects of underwater noise on the hearing sensitivity of three pinnipeds: a California sea lion (Zalophus californianus), a harbor seal (Phoca vitulina), and a northern elephant seal (Mirounga angustirostris). Temporary threshold shift (TTS), defined as the difference between auditory thresholds obtained before and after noise exposure, was assessed. The subjects were exposed to octave-band noise centered at 2500 Hz at two sound pressure levels: 80 and 95 dB SL (re: auditory threshold at 2500 Hz). Noise exposure durations were 22, 25, and 50 min. Threshold shifts were assessed at 2500 and 3530 Hz. Mean threshold shifts ranged from 2.9-12.2 dB. Full recovery of auditory sensitivity occurred within 24 h of noise exposure. Control sequences, comprising sham noise exposures, did not result in significant mean threshold shifts for any subject. Threshold shift magnitudes increased with increasing noise sound exposure level (SEL) for two of the three subjects. The results underscore the importance of including sound exposure metrics (incorporating sound pressure level and exposure duration) in order to fully assess the effects of noise on marine mammal hearing.
Kastak
David
D
Institute of Marine Sciences, University of California, Santa Cruz, Long Marine Laboratory, 100 Shaffer Road, Santa Cruz, California 95060, USA.
Southall
Brandon L
BL
Schusterman
Ronald J
RJ
Kastak
Colleen Reichmuth
CR
D000818:Animals; D001309:Auditory Threshold / Q000502:physiology*; D010872:Caniformia / Q000502:physiology*; D003213:Conditioning, Psychological; D004781:Environmental Exposure; D005260:Female; D006309:Hearing / Q000502:physiology; D008297:Male; D009622:Noise / Q000009:adverse effects*; D046049:Phoca; D011601:Psychophysics; D046070:Sea Lions; D046048:Seals, Earless; D014867:Water
D014867:Water