Enhanced sound insulation properties of microporous PMMA foams by constructing novel multilayered and directional cell structure (MDCS)

The main purpose of this study is to improve the performance of soundproofing materials through structure design without any functional phases. The sound insulation properties of PMMA microporous foams with multilayered and directional cell structure (MDCS) were investigated. The influence of the MDCS on sound transmission loss was discussed in detail. In addition, the mechanism for improving the sound transmission loss of the multilayered foams was discussed. The results show that the sound transmission loss value of the multilayered foams is up to 29.70 dB, which is 29.5% higher than that of the single‐layer foams. It is due to the MDCS, which reduces the cell size of the foams, leading to increase the reflection and scattering of sound waves in pores. Meanwhile, the MDCS accompanied by multilayer interfaces increases the multiple reflection of sound waves at the interfaces. Besides, the smaller cell size and higher cell density strengthen the stiffness of the foams, which promotes the sound insulation properties. This study presents a novel and convenient method to design modern sound insulation materials.