Effects of vibration magnitude and posture on seat-to-head-transmissibility responses of seated occupants exposed to lateral vibration

Abstract

In an attempt to define how train vibration and motion affect passenger comfort, an experimental study has been conducted to show the effect of variations in posture and vibration magnitude on head motion in three translational directions (fore-and-aft, lateral and vertical) with seat vibration in lateral direction. Thirty healthy male subjects were exposed to random vibration in lateral axis with three excitation magnitudes of 0.4, 0.8 and 1.2 m/s2 rms over the frequency range of 1-20 Hz. The data results are analysed in terms of seat-to-head-transmissibility response, phase and coherence for head motions in two sitting postures (backrest and forward lean). The seat-to-head-transmissibility response registered maximum head motion in lateral direction with single peak at 2 Hz in both the sitting posture. The response also reported an additional peak near 6 Hz in forward lean postures. The broad peak converged to a single peak at 2 Hz with reduction in seat-to-head-transmissibility response under the higher magnitude of lateral vibration, which was attributed to the softening effect of the human body. The STHT response yields only minimal effect on posture, particularly in the vicinity of the resonance only.