Our prototype was developed on an SGI Indigo 2 Extreme, connected to an Acoustetron II from Aureal/Crystal River Engineering and Roland Sound Modules. The Open Inventor graphics toolkit [Wernecke94] was expanded for classes (nodes) to support the spatial sound extensions, which were used for our virtual reality applications. Open Inventor is a superset of the VRML 1.0 standard [Bell et al. 95], which does not support sound or dynamic behavior of objects. For the sound extensions of Open Inventor, we followed the VRML 2.0 standard [Bell et al. 96], but added a node for sound sinks. This allows scenes to have multiple sinks and a sink which can be separated from the viewpoint.