Functional Design of Low-frequency Sound Absorption in Multidirectional Folded Honeycomb Resonant Metamaterials

To address the challenges of balancing low-frequency broadband noise reduction and lightweight design in aircraft cabin noise control within the aviation field, a design method for a multi-directional folded honeycomb structure (MFHS) acoustic metamaterial was proposed. The sound absorption unit of the MFHS was composed of a honeycomb cavity and a square insert tube. A theoretical sound absorption model was established based on the resonance principle, and the influence laws of three key structural parameters (the side length and height of the insert tube, and the length of the cavity) on the sound absorption performance were systematically investigated. The coupled performance of multiple units in parallel was analyzed to achieve broadband sound absorption. To better achieve the lightweight objective, a design method of multi-directional folding was adopted, and samples were fabricated using lightweight materials. Experimental results show that the fabricated MFHS sample achieves an average sound absorption coefficient of 0.85 in the frequency range of 400–1200 Hz, and the thickness of structure is only 35 mm, the areal density is as low as 7.04 kg/m^2. This realizes the synergistic design of low-frequency broadband efficient sound absorption and lightweight, offering a new idea for low-frequency noise control in the aviation field.