Compact acoustic metamaterials based on azimuthal labyrinthine channels for broadband low-frequency soundproofing and ventilation

We introduce a compact acoustic metamaterial designed for broadband soundproofing and ventilation within the low-frequency range. Our design features a transverse bilayer structure that consists of a central orifice surrounded by azimuthal labyrinthine channels. The interaction of transmitted sound waves from each region leads to Fano-like interference which enables to attenuate over 90 % of the incident sound energy across a broadband frequency range from 571 Hz to 1043 Hz. Moreover, the overall thickness of the acoustic metamaterial is just 30 mm, which is approximately 1/20 of the operating wavelength. The soundproofing efficacy of the designed model is validated through theoretical calculations, numerical simulations and experiments. The acoustic metamaterial proposed in this work may be applicable to various fields that demand simultaneous noise reduction and ventilation within limited spaces.