New-parallel connection of the Helmholtz resonator with embedded apertures for low-frequency broadband sound absorption

We designed/proposed kinds of new-parallel connections of the Helmholtz resonator with embedded apertures (HREAs). The design rule of the resonator, aperture, and length of the embedded hole has much influence on the sound absorption characteristics of the metamaterials. The multiple nearly perfect sound absorption peaks in a wide frequency band were obtained. The results show that by accurately balancing the coupling parameters of the new-parallel connection of the HREAs, the resonators can have continuous excellent sound absorption performance in multiple frequency bands. The frequency of the absorption peak can be controlled by adjusting the geometric parameters of the resonator, and the absorption bandwidth can also be flexibly adjusted with a fixed thickness. The working wavelength of the designed new-parallel connection of HREAs is approximately 57 times its total thickness (43 mm), and the average sound absorption coefficient can be as high as 0.8.