Sound insulation of flow-permeable biomimetic honeycomb structures with Helmholtz resonators

Abstract Effective low-frequency noise control in ventilated systems is a significant engineering challenge due to the trade-off between airflow and sound insulation. This study presents novel flow-permeable biomimetic honeycomb structures with tuned Helmholtz resonators and perforated faceplates to improve low-frequency sound transmission loss (STL) while maintaining ventilation. Two core design configurations were developed: one with tubular hierarchical elements (HBEP) and another with hexagonal hierarchical elements (HSSH1) at the cell vertices. Both designs, inspired by natural honeycomb geometries, balance structural strength, airflow, and acoustic isolation, with a conventional honeycomb panel as the baseline. Finite element simulations and impedance tube measurements compared the new designs to the baseline model. The integrated resonators were tuned for frequencies between 200 Hz and 1400 Hz, where conventional panels underperform. STL improvements of up to 14.2 dB and 13.4 dB were measured for HBEP and HSSH1, respectively. Good agreement between numerical and experimental data was observed, though experimental STL trends did not capture the sharp numerical peaks due to non-planar wave effects, boundary conditions, sealant effects, and fabrication limitations. The proposed design addresses noise control needs in HVAC ducts, ventilated enclosures, railway interiors, and other airflow-critical systems.