Investigation of the Impact of Spectral Cues from Torso Shadowing on Front-Back-Confusion and Perceived Differences along Cones of Confusion

Front-back-confusion effects have been found to occur for sound sources where localization cue differences are insufficient to distinguish between front-back symmetric positions. However, in positions below ear level, which are of increasing interest for virtual reality applications with binaural rendering, torso shadowing introduces additional localization cues. This paper investigates if and how those additional localization cues affect front-back-confusion effects and the perceptibility of vertical position differences. Analysis of spectral cues in HRTF measurements shows substantially stronger localization cue differences below ear level compared to above. Subjective listening experiments on binaural headphones confirm significantly increased perceptibility of differences between sound source positions. In conclusion, the results show reduced front-back-confusion and increased vertical localization accuracy at low elevations, which should be considered in binaural measurement and rendering systems. Furthermore, good agreement between spectral cue analysis and subjective results was found and hence indicates a way to explain and predict perceptual differences.