Perforation Enhances Sound Insulation in Plate Lattice Metamaterials.

Ventilated sound-insulating materials are desirable, yet porosity often weakens insulation by creating sound-leakage pathways. Here, we demonstrate a face-centered cubic (FCC) plate-lattice implementation in which perforation geometry is engineered to regulate the acoustic-airflow trade-off. Two symmetry-preserving perforation strategies, positioned at either the edge-node regions or the centers of the plate facets, are systematically investigated by varying perforation diameter and relative density. Experimentally validated, counterintuitively, several perforated lattices outperform their non-perforated FCC counterparts over multiple frequency bands. Further, a best-performing lattice achieves a peak transmission loss of up to 50 dB at around 2300 Hz, 19 dB higher than its closed-cell counterpart, while maintaining a broad 1700 Hz bandwidth with transmission loss above 20 dB and retaining measurable airflow of 5% relative to an unobstructed channel. Finite element pressure, velocity, and stress-field analyses are consistent with a Helmholtz-like pore-cavity response and higher-frequency cavity-mediated interactions contributing to the enhanced attenuation beyond the mass-stiffness-controlled response of the baseline closed-cell lattice. These acoustic contributions are further represented by a reduced-order transfer matrix model, providing an analytical framework. Overall, this work demonstrates an architecture-specific strategy for using perforation geometry to regulate sound insulation and airflow within FCC plate lattice metamaterials.