Development of a sound quality index for the wash cycle process of front-loading washing machines considering the impacts of individual noise sources

The objective of this study is to determine the effects of individual noise sources on overall sound quality during the wash cycle of a drum-type washing machine, and to build a sound quality index for laundry noise. To adjust each noise source independently, we synthesized virtual laundry noises from actual laundry noise together with isolated sources of dropping noise, water noise, motor noise and circulation pump noise. We used this virtual noise to conduct a listening test by customers, finding that the dropping noise has a decisive effect on subjective sound quality. We conducted multiple regression analysis of sound quality using statistical data processing. The reliability of the multiple regression index was verified by comparison with subjective listening results and index results of actual laundry noises. This study is expected to provide a guideline for the improvement of laundry noise.