Structural optimization of binder-free honeycomb ramie woven fabrics for enhanced low-frequency sound absorption: a sustainable alternative to synthetic materials

Binder-free honeycomb ramie woven fabrics were fabricated via hot-water desizing and systematically optimized through yarn density, layer architecture, and backing air cavity depth. The resulting triple-layer configuration with a 9 cm air gap delivers exceptional low-frequency absorption, averaging 0.68 over 125–1000 Hz with a peak of 0.93 at 875 Hz, surpassing most natural fiber absorbers. This performance stems from synergistic quarter-wavelength cavity resonance and multilayer viscous dissipation, not Helmholtz effects (>10 kHz). Acoustic response is governed by a trade-off among airflow resistivity, tortuosity, and porosity, with impedance grading achieved by low-resistivity surface layers for broadband enhancement. Critically, the fully desized, binder-free textiles exhibit retained acoustic and mechanical integrity after aging, alongside a 35% lower carbon footprint and full biodegradability compared with glass wool, establishing a sustainable alternative for noise control.