Conventional stereo audio material is often produced using amplitude panning techniques to achieve flexible positioning of sound sources with a limited number of loudspeakers. Consequently, for faithful playback the orientation and position of the listener are very restricted. If stereo audio is reproduced over virtual loudspeakers on headphones incorporating head-tracking, these position and orientation restrictions limit the realism and spatial accuracy of the reproduction. In this paper, it will be outlined that amplitude panning and the corresponding phantom sound sources cause spatial quality limitations for headphone rendering. A novel method to circumvent phantom imaging on headphones is presented and evaluated in a listening test.

Loudspeaker reproduction systems are subject to a compromise between spatial realism and cost. By simulating loudspeaker reproduction on headphones, the resulting spatial realism is limited accordingly, despite the virtually unlimited spatial imaging capabilities of binaural audio rendering technology. More particularly, phantom imaging as often used for stereo audio material intended for loudspeaker reproduction is subject to various restrictions in terms of loudspeaker positioning in simulated space. As a consequence, phantom imaging should preferably be avoided when simulating virtual loudspeakers over headphones, especially if head tracking is incorporated or if a wide sound stage is desired. A novel method is described to extract phantom sound sources from stereo audio content and convert these to sound sources in a virtual listening environment.