Tunable low frequency band gaps and sound transmission loss of a lever-type metamaterial plate

A novel metamaterial plate with subwavelength lever-type resonators is proposed to obtain low frequency broadband band gaps and good sound insulation performance. The band structure is theoretically derived, and the validity of the theoretical method is verified by the finite element method. The formation mechanisms of the band gaps are illustrated by the analysis of the effective dynamic mass density and group velocity. The effect of the lever ratio on the band gaps is analyzed. The results indicate that as the lever ratio increases, the first band gap shifts to lower frequencies, while the bandwidth is widened. Moreover, the sound insulation performance of the proposed metamaterial plate is evaluated via examining the sound transmission loss (STL). Compared with the metamaterial plates without lever accessories, the proposed metamaterial plates with a suitable lever ratio have better sound insulation performance at low frequencies.