An apparent location of a sound source is controlled in azimuth and range
to a listener of the sound using headphones by a range control block that
has variable amplitude scalers and a time delay and by an azimuth control
block that also has variable amplitude scalers and time delays. An input
audio signal is fed in to the range control block and the values of the
scalers and the taps on the delay buffers are read out of look-up tables
in a controller that is addressed by an azimuth index value corresponding
to any location on a circle surrounding the headphone wearer. Several
range control blocks and azimuth control blocks can be provided depending
on the number of input audio signals to be located. All of the range and
azimuth control is provided by the range control blocks and azimuth
control blocks so that the resultant signals require only a fixed number
of filters regardless of the number of input audio signals to provide the
signal processing. Such signal processing is accomplished using front and
back early reflection filters, left and right reverberation filters, and
front and back azimuth filters having a head related transfer function.