Low-frequency broadband absorber with coherent coupling based on perforated panel and space-coiling channels

Efficient broadband absorption of low-frequency sound via ultra-thin structure remains challenging due to the narrow-band property generated by the dispersive nature of resonance. In this study, we investigate the absorption mechanism of a component composed of a perforated panel and space-coiling channels through the coupling effect, acoustic impedance matching, and complex frequency analysis. In addition, the influence of geometrical parameters, resonance frequency intervals, and number of components in the coupled system on the band is investigated. Accordingly, the strategy for developing absorbers is to design individual components in the under-damped state by adjusting the geometrical parameters, then put together multiple components with different channel lengths in parallel. On the basis of this strategy, a low-frequency and broadband absorber is theoretically proposed and experimentally demonstrated, which can achieve broadband absorption from 250 Hz to 450 Hz. The design strategy has potential applications in low-frequency noise control engineering, such as plants, automotive and aerospace industries.