Development of resistance to hearing loss from high frequency noise.
Subramaniam-M; Campo-P; Henderson-D
Hear Res 1991 Nov; 56(1-2):65-68
The role of exposure frequency was investigated as it related to the development of progressive resistance to noise induced hearing loss. Six adult chinchillas were made monaural and exposed to an octave band of noise centered at 4 kilohertz (kHz) for 6 hours a day for 10 consecutive days at 85 decibels (dB) sound pressure level. Threshold measurements were made just prior to and after each exposure period. There were no significant post exposure threshold shifts at 0.5 or 1kHz. There was a 10dB shift on the first day at 2kHz; this was less than 5dB by 10 days. There was a 30 to 40dB shift for 4, 5.6 and 8kHz frequencies on the first day; this was reduced by 12dB at 4kHz and 24dB at 5.6 and 8kHz by 10 days. The threshold shift was found to be greatest on day one at all the tested frequencies. Thresholds returned to baseline values by 48 to 72 hours when exposures were discontinued. The results indicated that there was a decrease in threshold shifts with repeated exposures to high frequency noise. The authors conclude that toughening can be seen at high frequencies.
NIOSH-Publication; NIOSH-Grant; Hearing-impairment; Noise-exposure; Laboratory-animals; Sensory-thresholds; Noise-induced-hearing-loss; Hearing-threshold; Noise-frequencies
State University of New York, Buffalo, New York