Noise‐induced temporary threshold shift in marine mammals.

Abstract

In 1996, Dave Kastak and Ron Schusterman reported the first observations of noise‐induced temporary threshold shift (TTS) in a marine mammal [D. Kastak and R. J. Schusterman, “Temporary threshold shift in a harbor seal (Phoca vitulina),” J. Acoust. Soc. Am. 100, 1905–1908 (1196)]. Since that time, a number of studies have been conducted to characterize the effects of noise on the hearing abilities of pinnipeds and odontocete cetaceans. These studies compare hearing thresholds before and after subjects are exposed to intense sounds and relate feature of the noise exposure to the observed threshold shift. The results are analogous to data from terrestrial mammals, where TTS depends on the frequency, amplitude, duration, and temporal pattern of the noise exposure, as well as the hearing test frequency and the recovery time. This talk reviews the major findings related to the growth and recovery of TTS in marine mammals, with an emphasis on recent data from high‐frequency tonal exposures in bottlenose dolphins. The relationship between onset‐TTS levels across a range of frequencies and proposed auditory weighting functions will also be discussed. [Work supported by the ONR.]