The quantitative relation between sensory cell loss and hearing thresholds.
Hamernik-RP; Patterson-JH; Turrentine-GA; Ahroon-WA
Hear Res 1989 Apr; 38(3):199-211
The quantitative relation between sensory cell loss and hearing thresholds was examined. Data on hearing threshold shifts and cochlear hair cell loss collected on 420 chinchillas exposed to impulse, impact, continuous broad band, or octave band noise at sound pressure levels of 80 to 165 decibels (dB) over a 5 year period were analyzed. The data were used to develop mathematical models expressing the loss of outer (OHC) and inner hair cells (IHC) as a function of permanent threshold shift (PTS). PTSs of less than 5dB consistently caused significant losses of OHCs across all tested frequencies, 0.125 to 16.0 kilohertz (kHz). Loss of OHCs was most severe at 1kHz for low PTSs. As the magnitude of the PTSs increased a large peak of OHC loss developed around the 4kHz region. Most of the loss occurred in the first two rows of OHCs. Significant IHC loss did not occur until the PTSs exceeded 30dB. The loss of IHCs occurred primarily at 4kHz. The authors conclude that the data support the notion that severe pathological changes in OHCs are associated with the first 30dB of noise induced PTS.
In-vivo-studies; Laboratory-animals; Noise-induced-hearing-loss; Hearing-threshold; Histopathology; Dose-response; Noise-levels
Plattsburgh State University, New York