The effect on the temporary threshold shift in hearing acuity from combined exposure to authentic noise and hand-arm vibration

Abstract

This study examined and compared the effect on temporary threshold shift in hearing (TTS) in healthy subjects of noise and hand-arm vibration (HAV) combined and separately using controlled and authentic exposure conditions. This study also investigated the effect on TTS in hearing in relation to gender after such exposures. Twenty-two healthy subjects (11 men/women, mean age 22 years, range 18-31years) were exposed both separately and in combination with HAV (6.7m/s(2)), using vibrating handles and to noise (99dB(A)) using headphones, for 20min. The HAV and noise were reproduced from recordings from angular grinder in operation. Hearing thresholds at 1, 4, and 8kHz were measured before and up to 30min after exposure. Combined exposure to noise and HAV created significantly greater TTS in hearing than HAV exposure at 4 and 8kHz alone. After exposure to HAV, there was no significant change in hearing threshold. At 1kHz, there was a significant difference between noise and HAV exposure in TTS in hearing. There was no significant difference between combined exposure and noise exposure for any test frequency. There was no significant difference in TTS in hearing in relation to gender for 1, 4, and 8kHz for HAV, noise, or a combined exposure. The results indicate that there is no difference in the TTS in hearing after combined exposure compared to noise exposure alone. HAV exposure did not change the hearing threshold. The TTS in hearing did not differ significantly in relation to gender after HAV, noise, or combined exposure.