Conference article

We conducted a subjective evaluation experiment to determine the optimal frequency characteristics for a car audio system during vehicle travel . In this experiment; the car interior noise typically generated when a vehicle travels at a speed of 60 km/h was added to the experimental sound sources; and subjective evaluation was made of the sound passed through filters modifying the frequency characteristics. A total of 10 types of sound sources were used in the evaluation (narration; fusion; classic; J-pop; vocal; healing; nature; jazz; rock; and pop). Five levels of frequency characteristic filter (-5 to -9 dB/oct.); which augmented the bass in response to car interior noise; were used. The evaluation terms were 12 pairs of words related to sound quality; comfort; added value; and safety. Higher evaluation scores were given to items of palatability and safety in the vicinity of the -6 dB/oct. filter level; which augmented the bass to a level slightly below the frequency characteristic curve of the car interior noise (?-7dB/oct.); and to items of sound quality and added value at the -9 dB/oct. filter level. Factor analysis was also conducted; to identify comfort; sound field; and clarity factors. Based on these factors; the filter results were compared. Higher comfort and clarity factor scores were obtained in the vicinity of the -6 dB/oct. characteristics versus those of other filters. These results confirmed that taking frequency characteristics into account in the performance of a car audio system during travel is effective in improving car interior comfort.

Car audio system; comfort; car interior noise; subjective evaluation