The model of sound radiated from two connected rectangular enclosures consisting of one elastically supported flexible panel and five rigid panels is deduced by using Hamiltonian function and Rayleigh -Ritz method in this paper. By means of artificial springs along connected points of flexible panels, this model allows the consideration of a wide variety structure joint conditions. Numerical results on the radiation of sound are presented. These results are intended to investigate two main issues:one is that the direct force affects the radiation of sound more than the indirect force does, the other is that the translational stiffness at connected points affects the radiation of sound more than the rotational stiffness does.