Effect of tool handle diameter on temporary threshold shift (TTS) of vibrotactile perception

Abstract

Objective Temporary threshold shifts (TTSs) of fingertip vibrotactile perception were measured in a laboratory study to examine the effects of handle size in combination with vibration frequency, amplitude, and frequency weighting, on human responses to hand–arm vibration (HAV). Methods Ten healthy male subjects were exposed to two levels of HAV: 125 Hz–5.0 m/s 2 and 125 Hz–20.0 m/s 2 (represented as a combination of vibration frequency and rms acceleration) using two different handles (22 and 35 mm in diameter) excited with a shaker. A simplified version of method of limits were used to measure vibrotactile perception thresholds and TTSs were then calculated as the difference between fingertip vibrotactile perception thresholds measured before and after 5 min vibration exposure. Results At 125 Hz–5.0 m/s 2 vibration, the handle size significantly affected TTSs in fingertip vibrotactile perception. In contrast, the handle size did not significantly affect the TTSs at 125 Hz–2.0 m/s 2 vibration. Conclusions Our results suggest that handle size is more sensitive to the TTS in fingertip vibrotactile perception under relatively lower vibration level. From a viewpoint of risk assessment to HAV exposure, TTS after short-term exposure to HAV is indicative of HAV syndrome resulted from long-term exposure to HAV. Since the long-term effect has been the accumulation of repeated short-term effect of HAV, our results suggest that the tool handle size is recommended to be designed based on the vibration level so as to diminish TTS. Relevance to industry Results obtained from this study show that the range of handle diameter examined in this study does not have a significant influence on TTS in vibrotactile perception. This finding gives fundamental data to the designing of hand-held power tools.