A broadband sound-absorbing panel based on the coiled coplanar absorber with multiple absorption peaks

We report an ultrathin sound-absorbing panel with a continuous sound absorption greater than 0.7 over a frequency bandwidth of about 600 Hz. The panel is constructed by several different individual absorbers, and each absorber is composed of a perforated plate and a coiled coplanar air chamber with an extended tube inserted at the end of it. The extended tube which is co-planarly coiled in a plane with the chamber divides the end of the chamber into three tubes. By designing the geometric parameters of the three tubes, an absorption coefficient spectrum of the individual absorber with three absorption peaks can be designed, and every absorption peak can be adjusted individually. As the research premise of the broadband sound-absorbing panel, the acoustic absorption coefficient of the individual absorber is first derived through the theoretical method, and the fundamental effects of the structural parameters on the absorption characteristics are also investigated. Besides, the physical absorption mechanism of the absorber is also revealed by numerical simulation. Therefore, by connecting several absorber units with reasonable structural parameters in parallel, a parallel absorbing panel with broadband absorption bandwidth can be designed. To verify the validity of the designed individual absorber and the broadband absorbing panel, samples have been designed and fabricated by 3D printing, and their acoustic characteristics are measured by experimental study. (paper)