Stereo headphone sound source localization system

Apparatus for processing an input audio signal for playback over headphones in which an apparent source of the audio signal is located outside the head of the headphone user, comprising:

• azimuth processor means receiving the input audio signal and producing left and right processed output signals, said azimuth processor means including left and right filters having coefficients based on an azimuth angle of the apparent source of the audio signal relative to the headphone user;
• azimuth control means for producing a control signal fed to said azimuth processor means for controlling the azimuth angle in response to azimuth information contained therein;
• range processor means receiving the input signal and producing left and right processed output signals that are attenuated in amplitude to represent a range between the apparent source of the audio signal and the headphone user;
• range control means for producing a control signal fed to said range processor means for controlling an amount of the amplitude attenuation in response to range information contained therein;
• and
• left and right signal summing means connected to sum the respective outputs from said azimuth processor means and said range processor means and produce left and right summed output signals fed to respective left and right ear transducers of the headphones.

Apparatus for processing input audio signals for playback over headphones in which an apparent source of the audio signal is located outside of the head of the headphone user, comprising:

• range processor means receiving the input audio signals and producing outputs therefrom that are attenuated in amplitude to represent a selected range between the location of the apparent sound source and the headphone user;
• azimuth processor means receiving outputs from said range processor means and producing a first plurality of outputs therefrom having information imparted thereto relating to a selected azimuth angle between the apparatus location of the audio signal and the headphone user;
• delay buffer means receiving as an input signal an output from said range processor means for producing at a plurality of outputs the input signal having been delayed in time and attenuated in amplitude, said delay buffer means including a plurality of signal adders each for adding selected outputs of said delay buffer means and producing a plurality of outputs equal in number to said first plurality of outputs from said azimuth processor means;
• reverberation processor means receiving as in input signal the output from said range processor means fed to said delay buffer means for producing left and right reverberation outputs therefrom;
• a plurality of head-related transfer function filters respectively receiving said first plurality of outputs from said azimuth processor means and outputs from said plurality of signal adders in said delay buffer means and in which filter coefficients are set by said information relating to the selected azimuth angle;
• signal summing means receiving outputs from said plurality of head-related transfer function filters and said from said reverberation processor means for producing left and right summed signals fed respectively to left and right ear transducers of the headphones.