Reconfigurable acoustic metamaterial chamber for low-frequency noise mitigation

In this study, a new reconfigurable sonic crystal metamaterial chamber is proposed for noise mitigation. Each element of the sonic crystal is made on non-circular cross-section with built-in Helmholtz resonators. Numerical and experimental investigation of a single unit cell and the whole acoustic metamaterial chamber highlights the reliability and feasibility of the proposed sonic-crystal based meta-structure. Highly efficient sound insertion loss can be captured with a simple and easily accessed resonator. By carefully designing rotation support in each unit cell and manufacturing a 3-D printed base with periodic holes, the assembled resonators can be easily rotated, and the finite acoustic metamaterial chamber can be tuned to another configuration without the need of reprinting and redesigning the whole structure. By changing the configuration of the full chamber, the device can keep the insertion loss at a high level, while exhibiting a better ventilation ability. The reconfigurable, scalable, feasible, and controllable system can be easily applied to several practical scenarios like the silent zone in the city center, the ventilated noise isolate device for the machines, and the fully optically transparent ventilation sound-insulating structures.