A method and apparatus for producing virtual
sound sources that are externally perceived and positioned at any orientation in
azimuth and elevation from a listener is described. In this
system, a set of speakers is mounted in a location near the temple of a listener's head, such for example, on an eyeglass frame or inside a helmet, rather than in earphones. A
head tracking system determines the location and orientation of the listener's head and provides the measurements to a computer which processes audio signals, from a audio source, in conjunction with a
head related transfer function (HRTF) filter to produce spatialized audio. The HRTF filter maintains the virtual location of the audio signals / sound, thus allowing the listener to change locations and head orientation without degradation of the
audio signal. The audio
system of the present invention produces virtual
sound sources that are externally perceived and positioned at any desired orientation in
azimuth and elevation from the listener.