Extending perceived stereo baseline with vector-base amplitude panning and polarity inversion

We propose an extension to Vector-Base Amplitude Panning (VBAP) that simulates audio positioning beyond the physical baseline of a stereo speaker pair by introducing polarity inversion. The extension to VBAP, where audio sources are positioned on the line segment between loudspeaker vectors, refers to enabling panning outside the speaker positions, and thereby flipping the polarity of the signal from the opposite side speaker. The implementation allows for real-time processing. Listening experiments were conducted in a room with low reverberation on a pair of Bloomline Omnidrive Pro Mk II speakers, with eight participants who localized audio samples inside and beyond the stereo field. Results show that participants were able to perceive sound source positions up to 60% wider than the physical speaker span. The findings imply that by the polarity inversion VBAP can be generalised to, simulate audio positioning outside the speaker bounds and gives rise to a tool for creating virtual sound sources beyond the physical boundaries of the room in future immersive 3D applications.