Perceptual Band Allocation (PBA) for the Rendering of Vertical Image Spread with a Vertical 2D Loudspeaker Array

Abstract

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.

The Frequency and Loudspeaker-Azimuth Dependencies of Vertical Interchannel Decorrelation on the Vertical Spread of an Auditory Image

“…The results presented here suggest that the vertical localization cues from an elevated 8 kHz octave-band source have dominance over a lower positioned correlated source, when both are presented simultaneously. A large spectral notch around 8 kHz (caused by the pinna from the main-layer loudspeaker direction) is likely to be the cause of this effect, resulting in more energy for the 8 kHz band from the height-channel direction [35]. Furthermore, the downward extension following decorrelation suggests that both loudspeaker signals might be perceived independently at the same time, with the decorrelation process reducing the height dominance to "un-mask" the main-layer loudspeaker.…”

Sound Source and Loudspeaker Base Angle Dependency of Phantom Image Elevation Effect

“…The present author [23] showed the elevation effect for the phantom images of octave-band pink noises as well as for broadband pink noise for the 60…”

“…Voice of God) channels to provide an immersive listening experience. While the VBAP [35] is widely considered as a standard technique for 3D sound panning, new techniques for 3D sound recording [39][40][41] and upmixing [42][43][44] are being developed. Furthermore, the recently standardized MPEG-H 3D audio codec [45] offers a highly efficient, object-based coding and transmission of 3D audio for domestic broadcasting.…”

A Comparison between Horizontal and Vertical Interchannel Decorrelation

“…Another reason for a lack of significant VIS difference between the 'High' frequency band conditions in the subjective testing could be related to the "pitch-height effect" [24,26,27] and "directional bands effect" [28,29]. From the directional band research, it is known that 4 kHz and 16 kHz bands tend to be perceived in front and an 8 kHz band is often perceived above (if presented under anechoic conditions).…”

“…From the directional band research, it is known that 4 kHz and 16 kHz bands tend to be perceived in front and an 8 kHz band is often perceived above (if presented under anechoic conditions). Similarly, when octave-band noise signals are presented at ear height from in front of the listener, a "pitch-height effect" occurs which sees the 8 kHz octave-band elevated upwards (towards the position of the height-channel loudspeaker); whereas the 16 kHz band is localised towards the main-channel loudspeaker and 4 kHz is perceived somewhere between the two [24,26]. Wallis and Lee [27] have demonstrated that this effect also occurs when coherent octave-bands are presented in vertical stereophony, i.e., the same signal reproduced in a main-layer loudspeaker and a height-layer loudspeaker simultaneously (both of which are located in the median plane, similar to the test condition in the current experiment).…”