Abstract The instantaneous impression of the loudness of internal car noise was judged by using the method of continuous judgment by category. The effect of visual monitoring while driving and the habituation to noise were examined. The following results were found: (1) the instantaneous impression of loudness showed a high correlation with L Acq , which suggests that instantaneous loudness can be approximately estimated by L Acq , (2) visual information has a great effect on the impression of loudness; it was suggested that comfortable driving softens the sounds, while uncomfortable driving makes the impression of the sounds more negative; (3) in the group of subjects who tried the condition without visual monitoring after trying the condition with visual monitoring, the number of responses decreased; this suggests that, when other information about the change of sounds does not exist, habituation to sounds occurs with the elapse of time and it is reflected in the number of responses to noise events.