Composite structure with porous material and parallel resonators for broadband sound absorption at low-to-mid frequencies

Herein, a broadband acoustic metamaterial composed of parallel Helmholtz resonators (PHR) with embedded channels and porous material (PM), is designed for low-to-mid-frequency noise absorption. A theoretical model of acoustic impedance is developed to illustrate the absorption characteristics of PHR–PM. The validity of the present model is confirmed by comparing the experimental results and numerical simulations. The PM may enhance the sound absorption performance of the PHR–PM by satisfying impedance matching conditions, which provides a new strategy for designing resonant systems with tunable sound-absorption characteristics. Both PM and PHR contribute to sound absorption, although their absorption capacities depend on the frequency ranges. The effects of structural and material parameters on sound absorption capacity are also analytically explored. Results indicate that sound absorption in the co-action and PM-dominated regions is mainly affected by material parameters, while that across the entire frequency range is considerably affected by structural parameters. Moreover, the average absorption coefficient of the 13HRs–PM may reach up to 0.6 at the frequency range of 100–1600 Hz, demonstrating its potential in achieving good broadband sound absorption performance and excellent absorption tenability. The proposed novel composite structure offers a new strategy for realizing high sound absorption at low-to-mid frequencies.