Development of a light sound insulation structure with variable insulation performance by using inflated membrane. (Phase2: Practical structure)

Light wall structures with high sound insulation performance are required to be developed for houses and fuselage of vehicles. A new light sound insulation structure which is constructed with pressurized light inflated membrane bound by hard wire nets (Membrane Sound Insulator: MSI) was proposed and proved to have high sound insulation performance especially in low and middle frequency region according to its high rigidity, in the previous papers using small size test pieces. Moreover the sound insulation performance of MSI can be tuned by its air pressure. In this paper, in order to make sure the practicality of MSI, sound insulation performance of several kinds of MSI (Simple MSI) of practical size (600mmx600mm) were examined experimentally. And some composite structures with double panels and MSI (Composite MSI) were also tested to prove the superiority of MSI. A simulation method (the vibration model with 3 degrees of freedom + the transfer matrix method) was also proposed to estimate the sound insulation performance of Simple MSI and Composite MSI.