Hierarchical porous kapok fiber composite aerogel with Helmholtz resonant cavity for low-frequency sound absorption

The demand for advanced materials with low-frequency sound absorption, pressure resistance, and thermal insulation is increasing, particularly in aerospace, high-speed rail, and luxury automotive sectors. However, the functional limitations of current materials hinder their broader application in high-end industries. To solve this problem, this study combines a hierarchical porous biomass aerogel with a resonant cavity to create a Helmholtz resonance sound absorption structure. This design aims at achieving multiple functions, including low-frequency sound absorption, heat insulation, and pressure resistance capability. The sound absorption structure is composed of porous biomass aerogel instead of the traditional perforated plate and cavity. Among them, the hierarchical porous biomass aerogel is obtained from delignified kapok fiber and activated carbon crosslinked by gelatin. The influence of activated carbon concentration, resonant cavity depth and aerogel perforation rate on the low-frequency sound absorption effect in this aerogel is explored. The sound absorption structure demonstrates excellent low-frequency sound absorption performance. Additionally, the aerogel exhibits thin (the thickness of the aerogel material is 10 mm, the sound absorption structure is 30 mm), high compressive strength, and low thermal conductivity. This study provides a new idea for the preparation of multifunctional low-frequency sound absorption materials.