ACOUSTIC PERFORMANCE OF TUNABLE COMPACT ABSORBER

The recent development of acoustic metamaterials provides promising opportunities for developing highly effective sound absorber for low-frequency sound. However, when predicting the performance of these compact structures, the one-dimensional (1D) plane wave assumption and a uniform pressure distributing in the common junction are commonly applied, which becomes controversial to the ultrathin configurations of the existing metamaterials. This calls for the development of more reliable and accurate models to predict the acoustic properties of metamaterials. In this paper, a two-dimensional (2D) model for predicting the acoustic performance of a tunable compact absorber (TCA) is proposed based on sound radiation theory in a rigid-walled duct. The investigated TCA comprises multiple layers of microperforated panels (MPPs) and coiling up space. The sound absorption characteristics of the TCA are investigated via theoretical model and numerical model (finite element method). Consistent predicted results from both models manifest that the 2D theoretical model can accurately predict the acoustic performance of the TCA. To simultaneously achieve broadband noise damping, a parallel configuration of two TCAs with varying structural parameters is studied. Meanwhile, the coupling effects of the parallel configuration, which is always neglected in the literature are investigated. The numerical results reveal that the coupling effects weaken the absorption performance of the TCA at specific frequencies. These effects may become even more critical when a substantial number of components are utilized to enlarge the sound absorption band in the TCA or existing metamaterials. Our results provide new insights into the design of highly effective acoustic metamaterial for noise control engineering.