Effects of whole body vibration on outer hair cells’ hearing response to distortion product otoacoustic emissions
Whole body vibration (WBV) is one of the most vexing problems in industries. There is a debate about the effect of WBV exposure on hearing system as vibration-induced hearing loss. The purpose of this study was to investigate outer hair cells’ (OHCs’) hearing response hearing response to distortion product otoacoustic emissions (DPOAEs) in rabbits exposed to WBV. It was hypothesized that the DPOAE response amplitudes (Adp) in rabbits exposed to WBV would be lower than those in control rabbits not exposed to WBV. New Zealand white (NZW) rabbits as vibration group (n = 6, exposed to WBV in the z-axis at 4–8 Hz and 1.0 ms−2 root mean square for 8 h per day during five consecutive days) and NZW rabbits as control group (n = 6, not exposed to any WBV) were participated. Adp and noise floor levels (Lnf) were examined on three occasions: day 0 (i.e., baseline), day 8 (i.e., immediately 1 h after exposure), and day 11 (i.e., 72 h following exposure) with f2 frequencies ranging from 500 to 10,000 Hz and primaries L1 and L2 levels of 65 and 55 dB sound pressure level, respectively. Main effects were statistically found to be significant for group, time, and frequency (p < 0.05). DPOAE amplitudes were significantly larger for rabbits exposed to WBV, larger on day 8 and larger for mid to high f2 frequencies (at and above 5,888.50 Hz). Main effects were not statistically found to be significant for ear (p > 0.05). Also, four statistically significant interactions including time by ear, time by frequency, group by frequency, and group by time were detected (p < 0.05). Contrary to the main hypothesis, DPOAE amplitudes were significantly larger for rabbits exposed to WBV. WBV exposure significantly led to enhanced mean Adp at mid to high frequencies rather than at low ones.
KeywordsWhole body vibration Vibration-induced hearing loss Distortion product otoacoustic emissions Outer hair cell function Audiology
We would like to thank Professor Richard D. Kopke from the Department of Defense Spatial Orientation Center, Department of Otolaryngology for helpful comments and discussion in the preliminary steps of starting this project. This study was supported by the Tarbiat Modares University.
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