This paper studies how the sound distribution of room or cavity is affected by the boundary condition’s change. The boundary condition is assumed to be changed by putting sound absorptive material on walls. We also assume that the enclosure has low modal density, therefore individual mode participating in the response is important. What we have got from this study is that the patch placement is closely related to wave length, cavity size, and spacing of the patches. This provides us the guidelines that allow us to place the patch for achieving effective noise control. We believe that this can be used to reduce a car cabin or high speed train interior noise.