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Protection from noise-induced hearing loss in the noise-toughened auditory system.
1998 Midwinter Meeting Assoc Res Otolaryngology, St. Petersburg Beach, Florida, 1998 Feb; :336
The auditory system, toughened by an interrupted noise exposure, has been shown, in several reports, to be less affected by (or protected from) a subsequent high-level noise exposure. We report on a series of exposures that produce a 10 to 25 dB toughening effect across the 0.5 to 8.0 kHz test frequency range following exposure to a 115 dB peak SPL, 1 kHz narrow band (400 Hz) transient presented 1/s, 6hr/d for 10d. Following a 30d recovery period one group (N = 12) was exposed to the same impacts at 121 dB and another group (N = 12) at 127 dB. These higher level exposures lasted for five uninterrupted days and produced an asymptotic threshold shift (ATS). When compared to untoughened control subjects the toughened animals showed a statistically significant reduction of 10 to 25 dB in ATS levels across the entire test frequency range. There were, however, no statistically significant differences in the postexposure permanent effects measured at least 30 days following the ATS exposure. These results agree with our earlier data as well as that of Miller et al. [Acta Suppl. 176:191 (1963)] in demonstrating that threshold shift dynamics can be modulated without any subsequent protective effects.
Hearing-disorders; Noise-exposure; Hearing-loss; Analytical-processes; Noise-induced-hearing-loss; Laboratory-animals; Animal-studies; Animals
1998 Midwinter Meeting of the Association for Research in Otolaryngology
Plattsburgh State University, New York
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