Recently, quietness in passenger car compartment has been significantly improved. For getting more quietness without reducing the vehicle weight, it is necessary to adopt a new technical method based upon the objective evaluation of principal characteristic sound components which affect the impression of quietness and pleasantness at every driving situation.

In this study, for the purpose of developing a new objective evaluation method, we analyzed subjective evaluation of sound components (engine noise, booming noise, road noise and wind noise) of passenger car interior noise by using driving patterns including a variety of acceleration, deceleration and cruising. We clarified characteristic sound components which can be heard outstandingly at each element of the driving pattern, and we also obtained physical indexes for each sound component correlating subjective evaluation. By applying these indexes to passenger car interior noise, we can objectively estimate which sound component is heard outstandingly. We showed that engine noise and booming noise are dominant during acceleration, and a good balance of sound components is desired during cruising, and we gave a guide to make pleasant sounds. Also we examined the masking effect affecting the loudness of sound components.
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