An optimization approach to control sound source spread with multichannel amplitude panning

The perceived spread (or width) of a sound source is an important attribute of an audio object that should be controlled by a multi-channel audio reproduction system. It is desirable to either synthesize a plausible spread of a sound object or to maintain a constant spread when the virtual source moves. Existing sound spreading techniques such as Multiple Direction Amplitude Panning (MDAP) or time-frequency decomposition typically do not account for the specific loudspeaker arrangement and the inherent source spread generated by this layout. In this paper we propose an optimization-based sound field control approach, termed the `1/`2 method, to adjust the spread of a sound source. To this end we use the velocity vector magnitude to quantify the desired source spread. Based on the equivalence between amplitude panning and the maximization of this vector, the control of the source spread is formulated as a convex optimization problem. We show how the velocity objective function and additional constraints affect the resulting loudspeaker gain distribution. The proposed approach can be integrated into amplitude panning systems, and allows for either a position-independent spread of moving sources or for a smooth and continuous control of the spread parameter