Origami-based acoustic metamaterial for tunable and broadband sound attenuation

• A novel origami-based acoustic metamaterial (OBAM) was designed and fabricated. • OBAM's tunable and broadband TL capacity at low frequencies was demonstrated. • OBAM's thickness is only 1/18–1/6 λ with λ being the working wavelength. • OBAM allows airflow-permeating and owns high design flexibility and programmability. Noise reduction is of critical importance in many engineering applications. One way to achieve noise reduction is using acoustic metamaterials. However, traditional acoustic metamaterials have long been criticized for the fixed and narrow frequency band in low- and medium-frequency sound attenuation. In this study, by incorporating the accordion origami into Helmholtz resonators as the side cavity, a novel origami-based acoustic metamaterial (OBAM) with tunable and broad bandwidth sound-eliminating capacities is developed. The sound attenuation properties of the proposed OBAM, quantified by transmission loss ( TL ), are extensively investigated by theoretical, numerical, and experimental methods. The sound attenuation of the OBAM can be readily tuned by air pressure via capitalizing on the single-degree-of-freedom property of accordion origami. The transfer matrix method is used to compute the TL of the OBAM analytically, compared with those obtained from the finite element and acoustic impedance methods. Results show that the theoretical, numerical, and experimental methods have good consistency, and the TL can be easily and quantitatively tuned by pressure in the low-medium frequency band. The working frequency bandwidth ( TL larger than 10 dB), achieving an effective attenuation of more than 90% of the sound energy, can reach 500 Hz in the range of 271–790 Hz, in which the thickness of the OBAM is only 1/18–1/6 λ with λ being the working wavelength, demonstrating the powerful and broadband low-frequency sound elimination capacity of the OBAM at sub-wavelength. Moreover, the proposed OBAM allows airflow-permeating, possesses high design flexibility and programmability, and remains scale-independent, real-time tuning, and free of the complex control algorithm. This study paves the way for effective tunable and broadband sound insulation attenuation equipment with efficient ventilation.