Vibration-driven tunable acoustic absorber utilizing granular segregation

키워드

확장요약문

This study proposes a tunable acoustic absorber that controls sound absorption frequencies through vibration-induced granular segregation. A Helmholtz resonator embedded in a bed of lightweight particles moves upward or downward depending on the direction of vibration. Vertical vibration induces upward migration through the Brazil nut effect (BNE), while horizontal vibration causes downward migration through the reverse Brazil nut effect (RBNE). This reversible motion allows the position of the resonator to be controlled without changing its structure. Discrete element method (DEM) simulations demonstrate the migration behavior of the resonator within the granular bed, while acoustic simulations and impedance tube experiments confirm that changes in its position shift the sound absorption peak frequencies. The approach is further extended to multiple resonators, enabling selective tuning of multiple absorption frequencies. These results demonstrate that vibration-induced granular segregation provides a simple and effective mechanism for reconfigurable sound absorption.