Energy-independent factors influencing noise-induced hearing loss in the chinchilla model.
J Acoust Soc Am 2001 Dec; 110(6):3163-3168
The effects on hearing and the sensory cell population of four continuous, non-Gaussian noise exposures each having an A-weighted L(eq)=100 dB SPL were compared to the effects of an energy-equivalent Gaussian noise. The non-Gaussian noise conditions were characterized by the statistical metric, kurtosis (beta), computed on the unfiltered, beta(t), and the filtered, beta(f), time-domain signals. The chinchilla (n=58) was used as the animal model. Hearing thresholds were estimated using auditory-evoked potentials (AEP) recorded from the inferior colliculus and sensory cell populations were obtained from surface preparation histology. Despite equivalent exposure energies, the four non-Gaussian conditions produced considerably greater hearing and sensory cell loss than did the Gaussian condition. The magnitude of this excess trauma produced by the non-Gaussian noise was dependent on the frequency content, but not on the average energy content of the impacts which gave the noise its non-Gaussian character. These results indicate that beta(t) is an appropriate index of the increased hazard of exposure to non-Gaussian noises and that beta(f) may be useful in the prediction of the place-specific additional outer hair cell loss produced by non-Gaussian exposures. The results also suggest that energy-based metrics, while necessary for the prediction of noise-induced hearing loss, are not sufficient.
Noise-exposure; Hearing-loss; Etiology; Exposure-limits; Risk-factors; Animals; Laboratory-animals; Environmental-exposure; Statistical-analysis; Workers; Auditory-system; Sound
Roger P. Hamernik, Auditory Research Laboratory, State University of New York, Plattsburgh 12901
Journal of the Acoustical Society of America
Plattsburgh State University, New York