Multilevel plate-type acoustic metamaterials with level-to-level modal antiresonance for sound insulation

Abstract

With the goal of engineering applications, the scalability of plate-type acoustic metamaterials (PAMs) is significant. However, most of the designed large-scale PAMs are formed by extending a single PAM cell to an array of cells, which will inevitably introduce vibroacoustic behavior to the entire array structure, resulting in a decay of sound transmission loss (STL) performance in certain frequency bands. To overcome this weakness, we present a new conceptual design of a multilevel PAM to enhance STL performance again by considering level-to-level modal antiresonance. The modal antiresonance of the second-level PAM, which manifests itself as the coupling through out-of-plane vibration of the first- and second-level PAMs, is analyzed to reveal the physical mechanisms. In addition, we also find that the STL profile of the second-level PAM has different dependence on the masses placed on the PAM cell and PAM array. We theoretically design and experimentally demonstrate the sound insulation properties of the proposed second-level PAM. Since the configuration of the multilevel PAM can be easily and flexibly designed in accordance with actual application requirements, it has broad application prospects including but not limited to submarine shells, aircraft cabins, and transformer rooms.