A subwavelength absorber with labyrinthine structure and adjustable low-frequency properties

The investigation of sound absorption through metamaterials with deep subwavelength thickness has garnered significant attention in the field of noise control. In this paper, An adjustable low-frequency subwavelength absorber with a labyrinth cavity and embedded aperture is presented, in which the built-in plates is designed to be scalable. The structure enables nearly perfect absorption at a remarkably thin thickness of 12 mm, exhibiting an absorption coefficient of 0.99 at 243 Hz. Notably, the thickness of the designed structure amounts to only 1/117th of the longest operational wavelength. The sound absorption performance is thoroughly examined through both theoretical analyses and numerical simulations using COMSOL. Furthermore, the tunability of the acoustic absorber was analyzed based on the length and size of the aperture as well as the length of the built-in plates. significantly enhancing the system's ability to match impedance. This research may have applications in low-frequency acoustic absorption and offers insights for designing low-frequency acoustic absorbing metamaterials.