For every display frame, the left and right eye images are displayed alternately. Lightweight liquid crystal shutter glasses are worn by participants. These glasses activate each eye in succession. The user's movable elements emit high-frequency sound, detected by the collection of stationary microphones. Variation in signal strength among microphones indicates location of the sound source.
Acoustic tracking can be accurate to within a few millimeters.
In electromagnetic tracking, stationary elements emit a pulsed magnetic field. A movable sensor attached to the user reports position and orientation relative to the source. Electromagnetic tracking can be accurate to within 2.5 mm in position and 0.1 degree in rotation, although accuracy deteriorates with distance from the source. It is also susceptible to interference from metallic objects in the environment. These have a range of up to 10' in diameter.