Synergetic coupling large-scale plate-type acoustic metamaterial panel for broadband sound insulation

In the field of low-frequency noise control, the locally resonant membrane and plate-type acoustic metamaterials (PAMMs) have received extensive attention from researchers due to its sub-wavelength thickness and low surface density properties. However, the existing research works mainly focus on the sound transmission loss (STL) of small-sized unit cells with the fixed boundary, resulting in that the sound insulation performances are great different from those of the large-scale structures used in engineering applications. For this reason, a square large-scale PAMM panel with side length of 0.704 m, which consists of a periodic array of square unit cells, is numerically studied under the normal incidence condition. The results show that the large-scale PAMM panels appear the obvious STL peak (~38 dB) in the low-frequency range. Moreover, the goal of broadband sound insulation based on the multi-cells synergetic coupling is realized by reasonably arranging the masses on the metamaterial panels. Numerical results indicate that a broadband insulation with average STL higher than 20 dB is obtained in the range of 300–900 Hz. Finally, a simplified experimental setup based on the box and semi-anechoic chamber is designed to verify the sound insulation performance, and the experiment under standard reverberation chamber and semi-anechoic chamber is performed in order to evaluate the sound insulation capability in the actual reverberation noise environment. The ideal periodic boundary is used in the numerical calculations, which is obviously different from the boundary condition in experiments. Therefore, the influence of the boundary condition on the STL is discussed and analyzed by calculating the STL of the metamaterial panels with different number of cells. The proposed design methods and results can provide some guidance for the application of the PAMM panels in practical engineering.