Combined Effects of Noise and Hand-transmitted Vibration on Workers' Muscle and Mental Fatigues in a Simulated Construction Operation.

Abstract

The frequent use of hand-held vibrating tools by construction workers exposes them to hand-transmittedvibration (HTV) and noise. This study investigated the effect of combined exposure to HTV and noise on workers' fatiguesunder simulated work with a typical building destruction tool. The repeated measures study was conductedon 40 construction workers exposed to HTV (5 m/s2 rms with frequencies of 31.5, 63, and 125 Hz), HTV (10m/s2 rms- 31.5 Hz), noise (90 dBA), and concurrent exposure (noise (90 dBA) + HTV (10 m/s2 rms- 31.5 Hz)) withthe typical vibrating hand-held tool for 30 minutes. Electromyography signals determined each worker's fatigue levelin the Flexor digitorum superficialis (FDS) muscle in two pre- and post-exposure periods. The subjects also filled outthe visual analog scale to evaluate mental fatigue severity subjectively. The mean differenceof muscle fatigueparameters was significant in all scenarios except for the two scenarios of alone exposure to HTV (5 m/s2 -125 Hzand noise exposure (p-value < 0.05). The mean difference of mental fatigue in all scenarios except for the two scenariosof exposure to HTV (5 m/s2 -125 Hz) and exposure to HTV (5 m/s2 -63 Hz) was significant (p-value < 0.05). Themost differences in muscle fatigue parameters (Amplitude = 8.16±5.63, Mean frequency=-4.69±3.78) and mentalfatigue (4.97±2.38) were observed in the simultaneous exposure to noise and HTV. Noise exposurealone cannot produce remarkable effects on muscle fatigue but can aggravate the effects of vibrations as a consequenceof synergistic interaction. However, the role of noise on perceived mental fatigue was more dominant than the HTV.These findings should be considered to adapt the existing exposure limits to actual work conditions.