Seat-to-head transmissibility and reading discomfort of the seated subjects exposed to whole body vibration

Abstract

The transmission of vibration from the vibrating interface to various organs of the human body may influence their functioning during the vibration exposure. Therefore, an experimental study on a vibration simulator has been performed to find the effects of vibration on reading performance, and also to establish the relationship between seat-to-head transmissibility (STHT) with reading difficulty and reduction in reading performance. Twelve seated male subjects were exposed to sinusoidal vibration with three magnitudes (0.5, 1.0 & 1.5 m/s2 rms) at seven different frequencies (4, 5, 6.3, 10, 16, 20, and 25 Hz) in three independent directions (vertical, fore-and-aft, and lateral). The results show that three output measures-STHT, reduction in reading performance, and perceived difficulty in reading-are significantly affected by the frequency of vibration in each direction. All three measures have shown the peak at 4 or 5 Hz in three independent directions of vibration. Another peak at 25 Hz has also been observed for reduction in performance and perceived reading difficulty in vertical direction vibration. The results also show decrease in resonance frequency of the transmissibility with an increase in vibration magnitude, which represents nonlinear behaviour in biodynamic response by the human body.