A Compact Tunable Broadband Acoustic Metastructure with Continuous Gradient Spiral Channels

Sound‐absorbing structures, an effective measure to reduce vibration and noise, have always been the desirable research hotspot in scientific and engineering communities. However, the mutual restriction between ultrathin thickness and broadband sound absorption is the key issue that hinders its development. Herein, a compact tunable broadband acoustic metastructure with continuous gradient spiral channels is presented, which has the ultrathin thickness and can efficiently realize low‐frequency broadband sound absorption. Coiled‐up individual absorbers are introduced to constitute the acoustic metastructure. The continuous gradient spiral channels are formed by successively decreasing the effective spiral length of labyrinthine cavity to achieve efficient broadband sound absorption. It is showed in the results that the sound‐absorption metastructure coupled with eight individual absorbers maintains the excellent broadband sound‐absorption effect over 0.8 in the frequency range of 487–930 Hz and a deep subwavelength thickness of 37 mm. In addition, the highly efficient low‐frequency broadband sound absorption can be implemented in the target range of 480–990 Hz through optimizing the adjustable parameters such as the effective spiral length, cross‐section height, orifice radius, and the coupling number of single absorbers. Herein, inspirations and threads are provided for the compact tunable broadband sound‐absorption design of acoustic metastructures.