Quantification of coin falling sound quality of coin processing machine

Quietness is essential for living comfortably but various noise exist at around our living place. Coins falling sound of the coin processing machine is one the noise around us. This noise disturbs our conversations, and it causes tired feeing occasionally. The coin falling sound is unsteady sound and have various frequency characteristic during very short time. Hence, not only the sound pressure level but also the quality is considered to be important for the improvement. In this study, we focused on the sound quality of the coin processing machine and investigated the impression through subjective evaluation test. In order to quantify the impressions, various coin falling sounds were prepared and the participants evaluated the "loudness," "pitch," "discomfort," and "tired feeling." In the sound quality analysis, multiple regression analysis was applied to understand which sound factor affects largely to the discomfort and tired feeling. As a result, both "discomfort" and "tired feeling" were observed to be affected by "loudness" and "pitch." Especially, tired feeling was found to be affected more by the pitch of the sound than that of discomfort. From these results, the noise at high frequency band was clarified to be necessary to improve the sound quality.