Frequency band optimization of cavity-type metamaterials by acoustic split-frequency multiplexing

Abstract

This paper reports an experimental study on a cavity-type metamaterial for broadband sound absorption to break the one-to-one correspondence between back cavity and absorption peak. An acoustic valve composed of a thin plate and a concentrated mass was proposed to pass and block specific frequency sound waves. The results indicate that under the action of the acoustic valve, the unit cell of the metamaterial can obtain more absorption peaks than the number of physical back cavities. Finite element simulation shows that this mechanism can be attributed to acoustic split-frequency multiplexing in the back cavity. Specific parameters for the unit cell are optimized based on genetic algorithms. The consistent finite element simulation and experimental results indicate that the metamaterial with the acoustic valve can achieve efficient absorption performance at 150–550 Hz with a thickness-to-wavelength ratio of 1/28. This study provides valuable design strategies for cavity-type metamaterials to achieve broadband sound absorption.