Abstract: The influences of different rib numbers and its arrangements on low frequency passive sound insulation, the selection of active control strategy and active control effects of rib stiffened double-panel system are investigated numerically. The theoretical model of rib stiffened double-panel system is firstly established using a combined modal expansion and vibro-acoustic coupling methods. Then the above issues are analyzed in detail by numerical simulations. It is concluded from investigation that the number of the resonant modes of the ribbed plate will become smMler in the low frequency range of interest when the number of ribs increases or the location of the ribs approaches the middle of the base plate. This is helpful for improving the overall low frequency sound insulation of the system. As for the active method, the control efficiency and noise reduction obtained by cavity control strategy are better than that obtained by panel control strategy. Due to the complex coupling effects of the ribs, the active control effects become worse when the number of ribs increases or its location approaches the middle of the base plate. More secondary sound sources are needed in this case to gain preferable noise reduction.