On the Estimation of Psychological Stress Caused by Road Noise in a Vehicle Cabin

To achieve the human-adaptive active sound control in a vehicle cabin based on the pulse waves and electroencephalographs of passengers, the effect of psychological stress to them caused by the road noise is investigated. The experiments are performed based on the measured road noise in a small light vehicle and the psychological stress due to the control and change of the sound is studied by recording their pulse waves and electroencephalographs. Experimental results show that the psychological stress to the passengers can be clearly evaluated with pulse waves and electroencephalographs. Loud road noise causes the decrease of the ratio of low-frequency and high-frequency component of the time series of the period of R-waves in their pulse waves. Further, their alpha waves in their electroencephalographs are also decreased. They are also effective to evaluate their psychological stress caused by the sudden change of the road noise due to that of the roughness of the road surface. It is found that by decreasing the sudden change of the road noise around 120 Hz makes their psychological stress more light than decreasing it around 40 Hz from pulse waves and electroencephalographs. In addition, the results are well matched with those of impression evaluation.