Theoretical and numerical analysis on low-frequency sound transmission from façades into room

Regarding low-frequency sound transmission from building façades into room for outdoor noise, its mechanism is very complicated due to the combination of outer walls and windows, the vibration behavior of an entire building structure, and the acoustic coupling with an interior sound field. In particular, the installation of a double window system involves combined phenomena of its resonance transmission and normal modes of the room, which has not been fully understood. In order to investigate the phenomena, a theoretical examination is first conducted based on a one-dimension vibro-acoustic model assuming piston vibration of double windowpanes and air spring between them. Next, numerical simulations based on the vibro-acoustic FEM are performed for a house model that consists of outer walls and double windowpanes. The results are compared to clarify the effects of the thickness, stiffness and size of glazing and the air layer thickness for the double window, and also sound absorption of the room. Furthermore, the composite soundproofing effect of weight increasing of the outer walls and installation of the double window is examined to consider appropriate measures for low-frequency sound.