Double-leaf sound insulating wall is widely applied to cabins of air-plane or high-speed train, because transmission loss is larger nevertheless the weight is light. But transmission loss of double-leaf is decreased at the resonant frequency of the wall. So we tested resonators and tuned mass dampers to increase transmission loss at the resonant frequency. And we observed vibration modes of the surface of the wall and measured the transmission loss. Those results show that vibration modes which are generated by resaonators and mass tuned damper affect the sound transmission loss.
