Ultra-thin and ultra-lightweight meta-panel for low-frequency broadband sound insulation based on a computationally efficient design framework

• Ultra-thin/-lightweight meta-panel achieves low-frequency broadband sound insulation. • Theoretical model enables fast and accurate prediction of transmission loss (TL). • Physical mechanisms behind the meta-panel’s high insulation are identified. • Systematic design minimizes thickness (λ/464 at 100 Hz) and weight (1/40 of steel). • Experiments show up to 30 dB TL improvement over a same-weight conventional plate. This study proposes an ultra-thin and ultra-lightweight meta-panel designed for broadband sound insulation, particularly effective against low-frequency noise. The meta-panel consists of a multi-scale lattice structure sandwiched between two thin membranes, with geometrical parameters tuned to minimize both thickness and weight while achieving high sound transmission loss (STL) across a 100-1500 Hz range. A theoretical model is developed to rapidly and accurately predict the STL by integrating principal acoustic properties of the meta-panel, including the impedance of the membrane under elastic boundary restraints, derived using an equivalent acoustic circuit, and wave propagation through the multi-scale lattice, represented through parallel-arranged transfer matrices for the membranes and subwavelength channels. This model provides a computationally efficient framework for systematic optimization to reduce the thickness and weight of the meta-panel while preserving high STL, with negative effective mass densities and bulk moduli induced in different frequency bands. The optimized design has a thickness of 7.4 mm and an areal density of 1.73 kg/m², making it thinner ( λ /464 at 100 Hz) and 40 times lighter than an 8.9 mm thick steel plate with a comparable average STL in the low-frequency range of 100-500 Hz. Experimental validation using 3D-printed samples confirmed the theoretical predictions and demonstrated up to a 30 dB improvement in STL over a same-weight plate in the 100-500 Hz range, highlighting the meta-panel's superior weight-to-performance efficiency. The proposed meta-panel offers an effective noise insulation solution for applications where both thickness and weight reduction are essential, such as automotive, aerospace, and architectural industries.