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Interrupted noise exposures: threshold shift dynamics and permanent effects.

Authors
Hamernik-RP; Ahroon-WA
Source
J Acoust Soc Am 1998 Jun; 103(6):3478-3488
NIOSHTIC No.
20030548
Abstract
A parametric study of the reduction of threshold shift (toughening phenomena) that takes place during the course of an interrupted noise exposure is described. 266 chinchillas randomly assigned to one of 32 experimental groups were exposed to one of the following: a 400-Hz narrow-band impact noise having a center frequency of 0.5, 1.0, 2.0, 4.0, or 8.0 kHz and peak sound-pressure levels of 109, 115, 121, or 127 dB. The impacts were presented for 5 d, 24 h/d or for 20 d, 6 h/d. corresponding pairs of exposures had equal energy. Group mean noise effects were estimated from pure-tone threshold obtained form inferior colliculus evoked potentials and from surface preparation histology. The threshold shift (TS) toughening phenomena is shown to occur in response to all stimuli that produce a TS and at all audiometric test frequencies. The amount of toughening, which is limited to less than 35 dB, varies with noise frequency and intensity. Based on group mean data the auditory system is not protected from the permanent effects of an interrupted noise exposure as a result of the toughening effect but rather differences in permanent effects between the 5- and 20-d exposures are attributed to the spreading of the exposure energy over an extended period of time.
Keywords
Noise; Noise-exposure; Noise-frequencies; Noise-levels; Exposure-levels; Exposure-assessment; Audiometry; Auditory-system; Animals; Animal-studies; Hearing-threshold
Contact
Roger P. Hamernik and William A. Ahroon, State University of New York at Plattsburgh, 107 Beaumont Hall, Plattsburgh, New York 12901
CODEN
JASMAN
Publication Date
19980601
Document Type
Journal Article
Email Address
HamernRP@SPLAVA.CC.PLATTSBURGH.EDU
Funding Amount
2829511
Funding Type
Grant
Fiscal Year
1998
NTIS Accession No.
NTIS Price
Identifying No.
Grant-Number-R01-OH-002317
Issue of Publication
6
ISSN
0001-4966
Source Name
Journal of the Acoustical Society of America
State
NY
Performing Organization
State University of New York at Buffalo, Buffalo, New York
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