Industrial-scale manufactured acoustic metamaterials for multi-bandgap sound reduction

Abstract

Achieving mass manufacturability and convenient deployability is the cornerstone to enable the widespread adoption of acoustic metamaterials. This work is poised to address the current challenges associated with manufacturing and deploying acoustic metamaterials. The proposed acoustic metamaterials comprise the resonant and mounting parts assembled through stud-and-tube coupling. The resonant part consists of multiple unit cells connected by slender rods, and each unit cell contains four cantilever beam-type resonators with different geometric parameters for generating multiple bandgaps. The back side of the mounting part is flat and broad, facilitating the quick and secure attachment of the acoustic metamaterials on the surface of the host structure. The injection molding technique is employed to mass-produce the acoustic metamaterial specimens made of the Acrylonitrile Butadiene Styrene material. After that, the static mechanical characteristics of the acoustic metamaterial specimens are experimentally quantified by assessing the withstand tensile and compressive forces. Next, the underlying physics behind the dynamic mechanical characteristics of the acoustic metamaterial specimens are revealed by utilizing a combination of analytic, numerical, and experimental techniques. Finally, the acoustic metamaterial specimens deployed on a scaled-down aircraft cabin model are tested to verify the sound reduction effects in large-size and complex wave field environments. We find that the acoustic metamaterial specimens exhibit four complete locally-resonant bandgaps below 500 Hz, allowing multi-bandgap reduction of both air-borne and structure-borne noise. Our unique design of the multi-bandgap acoustic metamaterials and the practical prototypes manufactured at an industrial scale through injection molding represent a significant advancement toward the commercialization of acoustic metamaterials.