Multiscale porous with coiled-up channel for low-frequency broadband sound absorption

• A combination of the gradient perforated porous absorber and coiled resonator is studied. • The resonance of coiled-up channel intennsifies energy dissipation in porous materials. • Absorption performance is studied by theoretical models based on the transfer matrix method. • Parallel-connection unit cells achieve low-frequency broadband (211-3000 Hz) semi-sound absorption. A compact structure comprising the gradient perforated porous material and the coiled-up channel (GPPC) is proposed. The sound absorption performance is investigated by a theoretical model based on the transfer matrix method (TMM) and simulation with the finite element method (FEM), and the simulations are experimentally validated. Broadband absorption of porous material can be shifted to a lower frequency and enhanced by coiled-up channel of GPPC, which are due to the resonances of the meso-pore with coiled-up channel and the coupling effect of multiscale porous material and coiled-up channel, and the energy trapping between the meso-pore and porous material matrix. The effects of the geometry parameters of the meso-pore and coiled-up channel on the absorption properties are also discussed. Moreover, the absorption enhancement of GPPC relative to homogeneous porous relies on a proper porous material matrix. Finally, the GPPCs with a width and thickness of 70 × 100 mm is designed by parallel coupling, and the absorption coefficient exceeds 0.7 at [240, 3000] Hz, which is promising in engineering noise control and provides some preliminary understanding of the combination of the gradient perforated porous absorber and the coiled resonator.