Sound transmission characteristics of X-shape inertial amplification acoustic metamaterial

Abstract

This paper presents a new type of acoustic metamaterial plate periodically attaching X-shape inertial amplification (XIA) mechanisms to realize the low-frequency bandgaps and efficient sound insulation. Different from the conventional approaches relying on the mass law to reduce noise, XIA mechanisms mitigate the vibration, as well as the sound radiation, of the host structures by amplifying the inertia of the added small mass. The theoretical model of the XIA plate for computing the sound transmission loss (STL) and the band structure is verified numerically and experimentally. The results show that the XIA mechanism can open up transverse wave bandgaps in the band structure starting at a low frequency. The bandgap-induced attenuation of flexural vibrations significantly improves the STL performance of the host plate. However, the XIA mechanisms cause the early coincidence at the same time, showing an intersection of the real dispersion curve and the acoustic trace wave number curve in the band structure and a sharp valley in the STL curve. Parametric studies reveal that the amplification angle θ has the largest influence on the performance metric net STL gain G40dB. Moreover, increasing the amplification angle θ, the amplification ratio ξ, and reducing the amplification span d, can realize the STL peaks shifting towards low frequency. Finally, to expand application scenarios of XIA plates for sound insulation, two enhancement strategies of the multi-stage approach and the multi-mechanism approach are investigated.