Subjective experiment was conducted to investigate the effect of traffic noise on productivity. Multiplication tasks were assigned for one hour, and subjective votes were collected before and after the task. During the experiment, the cerebral blood flows of the subjects were measured. There were no significant difference in performance; however, the fatigue level was higher after subjects worked with traffic noise. The subjects also voted that it required more effort and they felt more frustrated to work with the noise. The cerebral blood flow significantly increased during the task with traffic noise, and the blood flow kept high even after the task ended.