A pneumatic soft acoustic metamaterial through modular design

Tunable acoustic metamaterials have excellent sound waves control and manipulation properties because of their deformations under different stimuli. Pneumatic actuation has recently attracted the attention due to its low-cost, fast in response and easy to integrate. However, due to the difficulty in fabricating soft enough scatterers and ensuring their airtightness, the experimental realization of pneumatic soft acoustic metamaterials remains a great challenge. In this paper, a pneumatic soft acoustic metamaterial is designed and its tunable band gap has been experimentally demonstrated. The designed pneumatic soft acoustic metamaterial comprises an array of soft inflatable rubber cavities in the background of air. And the scatterer in the soft acoustic metamaterials can deform by adjusting the air pressure, which can switch on or off the band gaps. The effects of scatterer shapes and orientations on the adjustable band gap are studied using numerical simulation methods. Furthermore, the modular design is introduced to ensure the flexibility of the designed soft acoustic metamaterials. And we fabricate modularized pneumatic soft acoustic metamaterials with square scatterers through the casting molding approach. The acoustic experiment results are agreement with the simulation results, which demonstrates that the band gap can be efficiently tuned when applying the air pressure. Additionally, the average transmission drops by about 20.2 dB in the maximum band gap of 3209.7–4639.7 Hz. This study provides a guide for designing and fabricating a pneumatic soft acoustic metamaterial, and confirms the feasibility and application potential of the design of acoustic devices by harnessing pneumatic actuation.