Optimal Crosstalk Cancellation for Binaural Audio with Two Loudspeakers

Crosstalk cancellation (XTC) yields high-spatial-fidelity reproduction of binaural audio through loudspeakers allowing a listener to perceive an accurate 3-D image of a recorded soundfield. Such accurate 3-D sound reproduction is useful in a wide range of applications in the medical, military and commercial audio sectors. However, XTC is known to add a severe spectral coloration to the sound and that has been an impediment to the wide adoption of loudspeaker-based binaural audio. The nature of this coloration in two-loudspeaker XTC systems, and the fundamental aspects of the regularization methods that can be used to optimally control it, were studied analytically using a free-field two-point-source model. It was shown that constant-parameter regularization, while effective at decreasing coloration peaks, does not yield optimal XTC filters, and can lead to the formation of roll-offs and doublet peaks in the filter’s frequency response. Frequency-dependent regularization was shown to be significantly better for XTC optimization, and was used to derive a prescription for designing optimal two-loudspeaker XTC filters, whereby the audio spectrum is divided into adjacent bands, each of is which associated with one of three XTC impulse responses, which were derived analytically. Aside from the sought fundamental insight, the analysis led to the formulation of band-assembled XTC filters, whose optimal properties favor their practical use for enhancing the spatial realism of two-loudspeaker playback of standard stereo recordings containing binaural cues.