Sound Transmission Loss of Acoustic Metamaterial with Lightweight Frame and Hard Membrane-Like Material

To reduce the noise in the frequency range of 100Hz~1000Hz, a metamaterial structure composed of lightweight frame, hard membrane-like material and added mass is proposed in this paper. The advantage of this structure is that it is lightweight and the membrane-like material does not need to be stressed in advance. Finite element method (FEM) and experiment are used to investigate the sound transmission loss (STL) performance of the metamaterial structure. The results show that the peak STL is caused by the local resonance of the added mass and the membrane-like material. The valley versus frequency results from the resonance frequencies of metamaterial structure, and it is divided into three resonance frequencies: resonance frequencies from added mass, membrane-like material and frame. Frame resonance will influence vibration of membrane-like material, if the frequency of frame resonance is close to the frequency at peak STL, the frequency at peak STL will be changed and the amplitude of STL at the peak will be lowered. The effects of the elastic modulus, density and width of the frame on the STL are discussed. The result shows that the STL is sensitive to frame width, and it is concluded that the effect of frame resonance on STL can be decreased by reducing the frame width, and STL is greater than 20 dB in the range of 400Hz-900Hz.