Multiband quasi-perfect low-frequency sound absorber based on double-channel Mie resonator

Metamaterial absorbers have recently been developed to act as efficient sound absorption components of subwavelength dimensions. However, the working frequency has so far been mainly limited to a single narrow band. Here, we demonstrate a multiband quasi-perfect absorber constructed by a double-channel Mie resonator (DMR) in a unique configuration. By attentively tuning the leakage factor to match the loss factor at multi-order monopolar and dipolar resonances of DMR simultaneously, a series of absorptive peaks with near-unity absorptances have been achieved in both numerical simulation and the experimental measurement. Our approach gives a simple platform for extending the response of metamaterial devices from the single band to the multiband without superimposing resonant elements in multiple configurations, which allows us to envision acoustic devices with versatile applications.