This paper describes the mutual effect between the sense of hearing and the sense of light on low frequency sound. Hearing thresholds were measured under the five kinds of lighting conditions; the steady lighting of 5000lx, 800lx, 0lx, flashed lighting of 5Hz and synchronized flashed lighting with sound. The hearing threshold under Olx illumination is the biggest ones among all lighting conditions. In order to inspect the reaction to low frequency sound with respect to the lighting conditions, psychological experiments were carried out with fifteen selected evaluation words under the five kinds of lighting conditions. The results were analyzed by the principal component analysis. The low frequency sound under the five kinds of lighting conditions was mainly evaluated by the two components; the total psychological intensity and the psychological component to express physiological sense. The two components are found to be related to the hearing thresholds.
In order to predict road traffic noise accurately, it is important to take account of the directivity of noise radiation from running vehicles. In this study, the directivities were measured by field experiment using three types of road vehicles and an approximate expression of the directivities was constructed by using regression analysis. Then the results were incorporated into the road traffic noise prediction model based on dynamic traffic flow simulation. To examine the validity of this model, road traffic noises in three urban areas were calculated by this model and the results were compared with the measured data. As a result, they were in good agreement. This fact indicates that the accuracy of the simulation program has been improved by taking account of the vehicle noise directivities.