The use of computer models for acoustical design of auditoria takes advantage of visualization and auralization for several purposes, some of which will be presented. The sound absorption characteristics of materials can be visualized by the use of colors of surfaces in a 3D room model. Calculation results displayed as color maps in a grid can give a quick overview of complicated conditions of sound distribution, including the display of acoustical parameters for noise level, sound strength, clarity, echo etc. The dynamic picture of a wave front with thousands of balls emitted from a source and reflected in a room has proven to be a useful tool to understand complicated conditions of sound reflection. Using auralization dynamic phenomena like reverberance, echo, and flutter echo can be auralized by listening to a hand clap. Coloration is another phenomenon that may be auralized by listening to white noise. The multisource auralization of a symphony orchestra where each single instrument has been modeled and auralized is a new technique which has opened for a detailed evaluation of the balance and blend due to reflecting surfaces near the orchestra.