Whole-body vibration: exposure time and acute effects — experimental assessment of discomfort

Abstract

The method of cross-modality matching was used to study the development of discomfort during a 1 hour exposure to whole-body vibration. The subject's task was to adjust a broadband noise to the level where it gave rise to the same degree of discomfort as a vibration. Random vertical vibrations were used with a resonance of either 3·1 or 6·3 Hz. The sound settings were transformed into vibration levels by means of sound-vibration functions determined for each subject. The sound-level settings increased as a function of exposure time and control measurements showed that this could not have been the effect of a lowered sensitivity to the noise. The increase, expressed as log acceleration, was a linear function of log exposure time. It is therefore concluded that results from studies of shorter exposure times might be extrapolated to exposure periods of at least 1 hour. Although the method employed probably led to an underestimation of the increase in discomfort over time, the experiment does imply that the increase is overestimated by ISO standard 2631.