An investigation on transmission loss of clamped doubled thin plate with added mass

Thin plate acoustic metamaterials (TAM) have demonstrated uncommon capacity in controlling low-frequency sound transmission. This paper concentrates on a theoretical and experimental investigation of clamped double polylactic acid (PLA) thin plates with attached mass. The theoretical formulation was done using a rectangular duct below the first cut off frequency. The sound transmission loss (STL) of the plates is calculated for plane wave condition, then the accuracy and capability of the theoretical model is verified through the comparison with the finite element method and experiment. The influence of several key parameters on the STL of the double-panel configuration is then systematically studied, including thickness of air cavity, magnitude of mass attached, and mode shapes. New peak and dip frequencies are found for the TAM with attached masses. The developed model can serve as an efficient tool for the design of such thin plate metamaterials.