Influence of SPL distribution on loudness impression for environmental noise

To realize comfortable living environment, it is necessary to reduce the environmental noise according to the suitable environmental noise evaluation index. For considering the environmental noise evaluation index, it is important to know characteristics of loudness evaluation toward long-term noise because the environmental noise was evaluated for long-term. In this study, to investigate the evaluation characteristics, we focused on the distribution of sound pressure level in duration of environmental noise and performed loudness evaluation test using long-term noise by changing the distribution. In the test, four traffic noises in duration of 10 min which loudness was adjusted equality by pre-processing were employed as base sounds. In addition, modified four noises in which the deviation of sound pressure level were increased (the mean value was same as the base sounds) were used as target sounds. Fourteen subjects evaluated the loudness of eight traffic noises immediately after hearing each sound. As a result, it was found that loudness impression toward the target sound was evaluated to as softer than the base sound. Consequently the long-term sound having large deviation of sound pressure level was clarified to be evaluated softer than the sound having small deviation.