Asymptotic threshold shift from impulse noise.
New perspectives on noise-induced hearing loss. Hamernik RP, Henderson D, Salvi R, eds. New York: Raven Press, 1982 Jan; :265-281
Efforts were undertaken to study impulse noise induced asymptotic threshold shift (ATS) and explore the systematic relationship between the intensity of the impulse and the level of ATS using adult chinchillas as the experimental animals. In one set of experiments the animals were exposed to impact noise of either 99, 106, 113, or 120 decibels (dB) peak sound pressure level. Impulses were presented at a rate of 1 impulse/second over 24 hours a day for 10 consecutive days. In the second set of experiments the animals were exposed to the same impulses but on a 7 day schedule such that after the seventh day, the impulse intensity was increased by 7dB for a total of 28 days until the 120dB level was completed. Auditory thresholds were measured in each animal at 0.5, 2.0 and 8.0 kilohertz daily during exposure. Findings indicated that impulse noise can produce a stable condition of ATS. The rate of growth to ATS appeared to be faster for impact noise than continuous noise, if the two types of noise were compared on the basis of their level of ATS. According to the authors, the relation between the level of the impact noise and the level of ATS is not simple. The discontinuity in this function probably reflects a shift in the destructive modes in the cochlea from primarily metabolic to actual mechanical disruption of the organ of Corti. The variability across animals is partially reduced in the ATS paradigm, but the variability is still a major problem, especially when compared to parallel studies using octave bands of continuous noise.
NIOSH-Grant; Noise-induced-hearing-loss; Laboratory-animals; Industrial-noise; Noise-exposure; Hearing-impairment; Acoustical-measurements; Acoustic-signals; Sound-analyzers; Auditory-system
Callier Ctr/communic Disorders Callier Center 1966 Inwood Road Dallas, Tex 75235
Hamernik-RP; Henderson-D; Salvi-R
New perspectives on noise-induced hearing loss
University of Texas Dallas, Richardson, Texas