Origami-inspired Acoustic Metamaterials: Real-Time Tunable Bandgap and Sound Attenuation

Conventional acoustic metamaterials possess a rigid configuration, precluding modulation of their sound absorption properties to adapt to complex, variable low-frequency noise environments. This study proposes an origami-inspired acoustic metamaterial (OriAM), featuring broadband, real-time tunable, and tailored bandgaps with low-frequency sound attenuation capabilities. The unit cell of the OriAM is derived from an accordion origami structure, endowed with flexible deformability, and integrated with a Helmholtz resonator. The accordion origami height of each unit cell can be real-time and dynamically regulated via pneumatic control to further manipulate the band structures and sound attenuation performance. The band structure and transmission loss of the OriAM are systematically investigated using the Bloch’s theorem, transfer matrix theory, and finite element analysis. It is demonstrated that the sound attenuation can be synergistically enhanced by both local resonance and Bragg reflection bandgaps. For a seven-unit-cell configuration, the effective noise attenuation bandwidth (sound energy attenuation greater than 90 %) can reach 1.85 octaves, enabling broadband mitigation. Bandgap properties and effective attenuation capacity can be also readily tailored by adjusting the 2D crease pattern parameters. Further investigation of the OriAM with gradient arrangement of unit cells reveals diverse acoustic phenomena, including spatial frequency division and wave field energy enhancement.