A new procedure for evaluating the impulse response between source and receiver locations in small reverberant rooms is outlined. The modified image method uses the solution of the Laplace transform based formulation for the Sommerfeld integral to determine the strength of image sources and boundary reflections. The model is used to simulate sound spatialization effects in small rooms. It is shown that spatial invariance of the poles in the room transfer function allows one to use IIR models for the long-time behavior of the impulse response. The variability of the short-time response with changing observation location is to be modeled using FIR models.