Metasurface by multiple perforated panels in a coiled arrangement

This study presents a hybrid acoustic metasurface by multiple perforated panels in a coiled arrangement, which exhibits superior broadband low-frequency sound absorption and rich tunability. The perforations were introduced on both the facesheet and coiled-up channels. The introduction of perforated holes into the channels not only can increase the acoustic dissipation, but also further compensate the acoustic reactance of the facesheet. A theoretical framework was set up to explain the inherent sound absorbing mechanism. Results show that the near perfect absorption frequency was dramatically reduced in comparison with the absorber without the inside perforations. A parametric study was subsequently carried out and confirmed the strong tunability of near-perfect sound absorption and relative absorption bandwidth. Experiments using an impedance tube were finally implemented and validated the theoretical findings. Superior absorption as well as deep-subwavelength thickness of this new hybrid acoustic metasurface paves the way in noise control engineering.