Propagation of the sound wave in a three-dimensional closed region is simulated in this study. The numerical method is based on wave equation. Since we intend to apply this numerical method to the simulation in the real concert hall, we adopt reflection condition and absorbing condition on the boundary. As for the former condition, we assume both free-end reflection and fixed-end reflection. On the other hand, we examine the modified equation which is obtained by adding viscous term to the wave equation in order to express the absorption on the boundary. The results are compared with those obtained by ordinal absorbing boundary condition. Using these method, the propagation of the sound wave is computed not only in the simple cubic region but also in a three-dimensional virtual concert hall.