US Patent 7095865 Audio amplifier unit

Face of a listener (user) is photographed by a CCD camera, and a face width and auricle size of the listener are detected on the basis of the picture of the listener's face. Head-related transfer functions, which are transfer functions of sounds propagated from virtual rear loudspeakers to both ears of the listener, are calculated, using the detected face width and auricle size as head shape data of the listener. Then, a filter process is performed by a DSP of a USB amplifier unit so as to attain characteristics of the head-related transfer functions, as a result of which sound image localization of the rear loudspeakers can be achieved via front loudspeakers.