Computer simulated sound propagation through 3D environments is important in many applications, including computer-aided de-sign, training, and virtual reality. In many cases, the accuracy of the acoustical simulation is critical to the success of the application. For example, in concert hall and factory design (where OSHA sound limits must be met), the accuracy of the simulation may save costly re-engineering after construction. In virtual environments, experiments have shown that more accurate acoustic modeling pro-vides a stronger sense of presence. Furthermore, auditory cues aid in formation of spatial impressions, separation of simultaneous sound signals, and localization of objects, such as when a soldier locates an enemy in a training exercise or a firefighter locates a person stranded in a burning building. In contrast, incorrect auditory cues can lead to negative training.