Temporary threshold shifts (TTS) of fingertip vibrotactile perception thresholds from hand-held tool vibration exposures at working surface

ObjectiveThe effect of hand-held vibration exposure in the working surface on the temporary threshold shift (TTS) in vibrotactile perception threshold at the fingers has been studied.MethodSubjects were exposed to the hand-held tool with the exposure time of 5 min at different positions in the working surface. A controlled condition with no vibration was included. In order to obtain the TTS in the fingertip vibrotactile perception threshold, the vibrotactile perception thresholds were measured before and after the subjects were exposed to hand-transmitted vibration from the hand-held tool.ResultsThe results of TTS were different at different positions in the working surface, even though the hand-held tool vibration magnitudes were the same frequency-weighted rms acceleration according to the ISO 5349-1 standard.ConclusionsEven though the tool vibration magnitudes were the same, the TTS values were different in the working surface. The results suggest that the ISO 5349-1 standard needs to be revised to include other factors that many influence the risk of obtaining a vibration-induced injury, such as posture.Relevance to industryResults from this study demonstrated the problem of the frequency-weighting method of the ISO 5349-1 standard in the working surface. Therefore, in the assembly lines or worktables of the industries, even though the tool position is in the working surface, the employees or employers must consider about the position of the tools to reduce the effect of vibration exposure for preventing the vibration injuries.