The calculating estimation of the initial impulse response at a receiving point within an auditorium through the computer simulation has developed as one of the effective measures to obtain design information for room acoustic designing. In simulating sound field in a room, it has generally been assumed to be a diffusive sound field. However, in analyzing the impulse response of a hall in terms of initial impulse response, which has a significant acoustic effect, the reflected sound from a wall surfaces reaches a receiving point discretely and not in a diffused state. Accordingly, such an assumption is not necessarily appropriate. This paper deals with the analysis of and experiments on the reflection response of finite rigid surfaces to acquire basic information for sound field simulation. In the analysis, the areal integrals on reflecting surfaces are found through the application of the sound ray tracing method, which has originally been developed on the basis of geometrical acoustics, for the approximation of impulse response incorporating the effect of the wave motion of sound. The appropriateness of the new finite sound ray integration simulation system is verified by proving the possibility of the approximation of a transfer function corresponding to the accuracy of simulation for the multiple reflection, through the comparative evaluation of the measured results and the results of simulation calculation regarding flat plate, diffusive plates and closed spaces.