Active Feedback Control on Sound Transmission Loss of Metamaterial Shell

In this research, the sound transmission loss (STL) through a metamaterial shell is studied and the active feedback control system is applied. The metamaterial shell consists of double cylinders connected by two four-truss mechanisms with the active control system. The space harmonic expansion method is used and the principle of virtual work is employed to derive the dynamic effective parameter and transmitted acoustic field. The expression of sound transmission loss is obtained to show the influence of active feedback control. Numerical results denote that the metamaterial shell can enhance the negative effective density and improve sound transmission loss within broadband regions. Moreover, the finite element simulation and experiment in the anechoic room are performed to support the theoretical predictions. These results are expected to provide useful vibroacoustic coupling structures for new aircraft.