Perceptual band allocation (PBA) for the rendering of vertical image spread with a vertical 2D loudspeaker array

Two subjective experiments were conducted to examine a new vertical image rendering method named "Perceptual Band Allocation (PBA)," using octave bands of pink noise presented from main and height loudspeaker pairs. The PBA attempts to control the perceived degree of vertical image spread (VIS) by a flexible mapping between frequency band and loudspeaker layer based on the desired positioning of the band in the vertical plane. The first experiment measured the perceived vertical location of the phantom image of each octave band stimulus for the main and height loudspeaker layers individually. Results showed significant differences among the frequency bands in perceived image location. Furthermore, the so-called "pitch-height" effect was found for two separate frequency regions, with most bands from the main loudspeaker layer perceived to be elevated from the physical height of the layer. Based on the localization data from the first experiment, six different PBA stimuli were created in such a way that each frequency band was mapped to either the main or height loudspeaker layer depending on the target degree of VIS. The second experiment conducted a listening test to grade the perceived magnitudes of VIS for the six stimuli. The results first indicated that PBA could significantly increase the perceived magnitude of VIS compared to that of a sound presented only from the main layer. It was also found that the different PBA schemes produced various degrees of perceived VIS with statistically significant differences. The paper discusses possible reasons for the obtained results in details based on the localization test results and the frequency-dependent energy weightings of ear-input signals. Implications of the proposed method for the vertical upmixing of horizontal surround content are also discussed.