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 (A(dp)) 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. A(dp) and noise floor levels (L(nf)) 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 f(2) frequencies ranging from 500 to 10,000 Hz and primaries L(1) and L(2) 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 f(2) 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 A(dp) at mid to high frequencies rather than at low ones.

BackgroundWhole body vibration (WBV) is a potentially harmful consequence resulting from the dissipation of energy by industrial machineries. The result of WBV exposure on the auditory system remains unknown. The objective of the present research was to evaluate the influence of WBV on cochlear function, in particular outer hair cell function. It is hypothesized that WBV impairs cochlear function resulting in decreased Distortion Product Otoacoustic Emission (DPOAE) levels (Ldp) in rabbits subjected to WBV.MethodsTwelve rabbits were equally divided into vibration and control groups. Animals in vibration group were exposed to 1.0 ms-2 r.m.s vertical WBV at 4–8 Hz for 8 h/day during 5 consecutive days. Outer hair cell function was assessed by comparing repeated-measurements of DPOAE levels (Ldp) across a range of f2 frequencies in rabbits both exposed and unexposed to WBV. DPOAE level shifts (LSdp) were compared across ears, frequencies, groups, and times.ResultsNo differences were seen over time in DPOAE levels in the non-exposed rabbits (p = 0.082). Post-exposure Ldp in rabbits exposed to WBV were significantly increased at all test frequencies in both ears compared to baseline measures (p = 0.021). The greatest increase in Ldp following exposure was seen at 5888.5 Hz (mean shift = 13.25 dB). Post-exposure Ldp in rabbits exposed to WBV were not significantly different between the right and left ears (p = 0.083).ConclusionWBV impairs cochlear function resulting in increased DPOAE responses in rabbits exposed to WBV. DPOAE level shifts occurred over a wide range of frequencies following prolonged WBV in rabbits.

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