Effects of Vibration on Seated Human Drowsiness/Alertness

Drowsiness is one of the major hazards to cause transportation accidents. To prevent the problem of drowsiness during driving, the relationship between the vibration and drowsiness is needed. This project aims to study on the effect of the vibration on seated occupants. The Heart Rate Variability (HRV), and the subjective sleepiness scale methods are used to measure the objective and the subjective alertness/drowsiness level of human. The HRV analysis relates to the activities of the sympathetic nervous system (SNS) and parasympathetic nervous system (PNS) . Both SNS and PSNS have mappings in HRV data – low frequency (0.04-0.15Hz) band power and high frequency (0.15-0.4Hz) band power. Thus, the LF/HF ratio is an index of human drowsiness/alertness. A higher LF/HF ratio means that SNS is more active and the human is more alert. Research Results The HRV data of the ten subjects show that their LF/HF ratio changes significantly after the vibration start which means the participants sleepiness level changed. This finding is also proved by the participant subjective feeling of the vibration. The average data of 10 participants’ LF/HF ratio data have significant fluctuation under vibration condition, and the data for control condition is flatter. This confirms that the participants alertness level varies significantly because of the vibration. However, the data indicate that the sensitivity of the participants to the vibration are different.