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. A head
tracking system determines the location and orientation of the listeners
head and provides the measurements to a computer which processes audio
signals, from an 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 user.