The main technology area that requires attention concerns the computer generation of sounds: software and hardware are required to enable VE system users to specify and generate the desired acoustic behavior of the objects and agents in the VE under consideration. Physical modeling of environmental sounds, together with the development of appropriate mathematical approximations and software and hardware that enables such sounds to be computed and rendered in real time, constitutes a major task in this area. Subsequently, it will be necessary to develop a user-friendly system for providing speech, music, and environmental sounds all in one integrated package. And eventually, of course, the whole sound generation system will have to be appropriately integrated with the software and hardware system for generating visual and haptic images. Compared with these sound generation problems, most of the remaining technological problems in the spatialization area for both HMDs and off-head displays appear relatively minor. It should be noted, however, that current technology is still unable to provide interactive systems with real-time rendering of acoustic environments with complex, realistic room reflections.