Variation of Floor-to-Head Transmissibility in Seated Human during Prolonged Driving Simulation

Abstract

In this study, the effects of prolonged exposure to whole-body vibration (WBV) on human physical response were investigated. In the experiments, the eight male subjects participated in a two hour driving simulation while being exposed to vertical random vibration. Five transmissibilities were obtained at thirty-minute intervals throughout the simulation. As the subjects viewed the driving simulation on a screen, they controlled the speed and direction with pedals and a steering wheel, respectively, although the vibration was stable and independent of the driving operation. Transmissibility was evaluated as the root-mean-square of transmissibility (T_rms), which was introduced to assess the amplitude of transmissibility within the frequency range of interest. The results showed that T_rms of the head transmissibility in the z-axis over time does not change significantly at the frequency range of interest (2-8 Hz) and that the change in T_rms depends on the test subject. However, when the magnitude of T_rms at the end of the two-hour driving simulation ("120 minutes") is compared with that at the beginning ("0 minute") in the same frequency band (2-8 Hz), T_rms tended to decrease over time. In particular, a significant difference between the two conditions was observed in the vicinity of the ±10% frequency range around the natural frequency. In addition, the changes in T_rms under conditions of with and without vibration were compared. Although the head transmissibility changed after exposure to WBV, the head transmissibility without vibration exposure showed no significant change.