STUDY OF SEATED HUMAN UNDER LOW FREQUENCY VIBRATION

Abstract

Humans are exposed to whole-body vibration in many types of environment. In almost all cases, the vibration to which the human is exposed comprises multi-axis vibration, such that vibration occurs in all directions simultaneously. Despite the complex nature of vibration to which humans are exposed in the workplace, almost all laboratory studies investigating the biomechanical response of the person have been completed using single-axis simulators. This project presents a study whereby 6 male subjects were exposed dual-axis vibration in the xz - direction using a 6 degree-of-freedom vibration simulator. All vibration magnitudes were 0.4,0.8,1.2 ms2_ rms in each axis. Subjects sat in two postures ('back-on' and `back-off) on a flat rigid seat. STH transmissibility dual-axis vibration stimuli showed. All results were in agreement with data previously published using single-axis vibration. In most cases, the peaks in the STH transmissibility occurred at a slightly lower frequency for the dual-axis vibration than for the single-axis vibration. It is hypothesised that this change is due to a nonlinear effect, analogous to that which occurs with increasing vibration magnitude for single-axis vibration. It is also observed that weight and height have a considerable effect on transmissibility.