Tunable acoustic metamaterial using length-variable labyrinth for broadband soundproofing and ventilation

We propose a tunable acoustic metamaterial that enables broadband soundproofing and ventilation while maintaining a consistent external geometry. It is meticulously engineered to induce Fano-like interference between continuous-state sound waves from a central orifice and discrete-state waves from surrounding azimuthal labyrinths. Building on the principle that the physical length of the labyrinthine channels critically determines the attenuation region of Fano-like interference, the structure consists of two distinct components: a front body with labyrinthine channels and a rotatable rear body with partitions. By simply rotating the rear body, the length of the channels can be adjusted, allowing tunability without altering the external geometry. This rotating-based mechanism enables over 95% attenuation of incident sound energy across a broadband frequency range from 587 to 1741 Hz. The variation in soundproofing efficacy with respect to the rotating angle is investigated through theoretical analysis, numerical simulation, and experimental measurement, confirming the tunability of the design. This reconfigurable metamaterial lends itself to practical applications that require simultaneous tunable noise control and ventilation.