Low-frequency sound-absorbing metasurface with a channel of nonuniform cross section.

In this letter, we propose a theoretical description of double nonuniform cross-section (DNUCS) channels, which can achieve the designed absorption coefficient with a shorter channel overall. Introducing channels with a nonuniform cross section changes the period of the surface acoustic impedance, which has a significant impact on the dominant operating frequencies. In this paper, we give the relation between the absorption peak position and the geometric parameters, which can be used to design DNUCS channels with a specific operating frequency. Furthermore, multiple nonuniform cross-section channels can be studied in the same way. Based on the above theory, we reduce the operating absorption frequency range of a new type of Fabry–Pérot absorbers to a lower regime in a constant volume. Our theoretical framework may be important in designing absorption metasurfaces and for further research. [ABSTRACT FROM AUTHOR]