Broadband low-frequency sound insulation of double-panel metastructures with a perforated lattice truss-core sandwich plate

Lattice truss-core sandwich plates have drawn increasing attention owing to their excellent mechanical properties and multifunctional characteristics, but they are insufficient in low-frequency sound insulation because of their lightweight feature. To improve the sound transmission loss (STL) of such lightweight sandwich plates while without greatly increasing the structural complexity and the total mass, one faceplate of the sandwich plate is perforated so that the sandwich core can be utilized as an acoustic cavity. A homogenous plate is further introduced to construct a double-panel metastructure together with the perforated sandwich plate. For ease of analysis and design of the double-panel metastructure, a semi-analytical method is developed by combining an effective medium theory of the acoustic domain and a dynamic homogenization method of the sandwich plate. The feasibility of the developed method for efficient STL prediction under different incident angles is verified by comparing with the conventional finite element method. Numerical results show that the double-panel metastructure exhibits a remarkable sound insulation performance within a broadband low-frequency range, owing to the fact that the acoustic domain enclosed by the double-panel metastructure has an unusual equivalent bulk modulus. Then, a parametric study is conducted to reveal the sound insulation capacity and provide a guideline for tuning the STL of the double-panel metastructure. Finally, the actual sound insulation capacity of the double-panel metastructure is validated by experimental measurements of large-scale specimens.