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Hazardous effects of noise on hearing.

Authors
Bohne-BA; Clark-WW
Source
Proceedings of Inter-Noise 87: Noise Control in Industry, Beijing, China, September 15-17, 1987. Beijing, China: Acoustical Society of China, 1987 Sep; :905-909
Link
NIOSHTIC No.
00232173
Abstract
The chinchilla was used as an animal model in a study of the relation between noise exposure and hearing loss. Groups of chinchillas were exposed to noise while systematically varying the intensity, duration and scheduling of the exposures. Some of the animals were trained in a behavior response mode prior to exposure. Exposure to low frequency noise at 75 to 95 decibels sound pressure level caused permanent structural damage within the outer hair cells (OHCs). The damage initially began in the low frequency region of the cochlea but did not produce a permanent threshold shift for low frequency tones until the loss of apical OHCs exceeded 30%. Exposures of 9 days or longer caused additional damage in the high frequency region of the cochlea. These lesions were initially quite narrow but involved losses of inner hair cells (IHCs), OHCs, supporting cells and auditory nerve fibers. When the chinchillas were given 18 hours of rest between successive 6 hour exposures, loss of the apical OHCs was reduced somewhat from that associated with a continuous exposure of equal energy, and the development of a low frequency hearing loss was delayed. An 18 hour rest between exposures provided no protection from cell loss in the basal turn of the cochlea or from the development of permanent threshold shifts for high frequency tones. The authors suggest that these findings may explain why a 4 kilohertz notch is usually the initial manifestation of hearing damage in workers from noisy industries, regardless of the frequency content of their exposures.
Keywords
NIOSH-Grant; Noise-induced-hearing-loss; Laboratory-animals; Ear-disorders; Noise-exposure; Industrial-noise; Noise-frequencies; Noise-levels
Contact
Research Central Inst for the Deaf 818 South Euclid St Louis, MO 63110
Publication Date
19870101
Document Type
Conference/Symposia Proceedings
Funding Amount
1063373
Funding Type
Grant
Fiscal Year
1987
NTIS Accession No.
NTIS Price
Identifying No.
Grant-Number-R01-OH-002128
Priority Area
Hearing Loss
Source Name
Proceedings of Inter-Noise 87 Conference, Beijing, China, September 15-17, 1987
State
MO
Performing Organization
Central Institute for the Deaf, Saint Louis, Missouri
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