Low-frequency sound absorption performance of composite acoustic metamaterials with rotational labyrinth channels and micro-perforated panels

In this paper, a kind of novel acoustic metamaterial combined with a rotational labyrinth and a micro-perforated plate is designed. The design of the rotational labyrinth structure combined with micro-perforated plates endows the acoustic metamaterial with excellent sound absorption performance. After in-depth study, it is found that the acoustic metamaterial has two sound absorption peaks in the range of 100–1300 Hz, the first sound absorption peak frequency is as low as 180 Hz, the sound absorption coefficient is more than 0.8 in the range of 210–300 Hz, and the sound absorption performance is relatively ideal in the middle and low frequency band. In order to further study the sound absorption mechanism, this paper deeply analyzed the sound pressure pattern diagram of the acoustic metamaterial under the sound absorption peak and carried out a theoretical calculation by using the transfer matrix method. Compared with the calculation and simulation results, the sound insulation mechanism at the first sound absorption peak was deeply studied, and experimental samples were obtained by 3D printing technology for physical experiments. The experimental results were found to be basically consistent with the simulation data. The correctness of the theoretical calculation and simulation is proved, and the practical engineering application value of the material is demonstrated. Finally, based on the sound absorption mechanism of the acoustic metamaterial, several factors were studied in depth. It is found through research that increasing the thickness of the micro-perforated panel reduces the sound absorption performance of the acoustic metamaterial but causes the first sound absorption peak to shift toward the low frequency band, while increasing the pore diameter of the micro-perforated plate and the length of the labyrinth channel could effectively improve the sound absorption coefficient. In addition, it is proved again that in this type of acoustic metamaterial, the micro-perforated plate mainly determines the sound absorption performance at the first sound absorption peak, and the sound absorption performance at the second sound absorption peak is mainly determined by the rotational labyrinth channel. The acoustic metamaterial can be obtained by setting parameters according to the actual requirements, which provides a novel design idea for the design of acoustic metamaterial and has important engineering application value.