Hearing loss in the chinchilla from impact and continuous noise exposure.
The relative hazard posed to the peripheral auditory system by impact/impulse and continuous noise of the same power spectrum was determined. Impact noise was generated by striking a nail with a hammer and was digitally recorded. The acoustical power spectrum of the impact was determined and pink noise was filtered to produce a continuous noise stimulus with the same acoustic power spectrum. Pre-exposure auditory evoked response (AER) thresholds were obtained at 1, 2, 4, and 8 kHz on 16 adult chinchillas. The pool of animals was divided into two equal groups based upon pre-exposure AER thresholds. One group was exposed to impact noise and the other group to the filtered pink noise. Exposures were 4 h/day for 5 days. Thirty days following the exposure, auditory evoked response thresholds were remeasured. Changes in auditory sensitivity were determined by subtracting the pre-exposure thresholds from the post-exposure thresholds. Hearing threshold shifts of the impact noise group were significantly greater (p less than 0.0001) than the hearing threshold shifts of the continuous noise group. These data indicate a need to more closely examine the parameters and effects of impact noise. There may be a need to develop expanded damage-risk criteria for occupational exposure to impulse/impact noise.
Dunn
D E
DE
U.S. Department of Health and Human Services, Centers for Disease Control, National Institute for Occupational Safety and Health, Cincinnati, Ohio 45226.
Davis
R R
RR
Merry
C J
CJ
Franks
J R
JR
D000818:Animals; D001303:Auditory Cortex / Q000503:physiopathology; D001305:Auditory Fatigue / Q000502:physiology; D001309:Auditory Threshold / Q000502:physiology*; D002682:Chinchilla; D006317:Hearing Loss, Noise-Induced / Q000503:physiopathology*; D008144:Loudness Perception / Q000502:physiology; D009622:Noise / Q000009:adverse effects*; D010898:Pitch Perception / Q000502:physiology; D013018:Sound Spectrography