Abstract
It is commonly believed that near-field head-related transfer functions (HRTFs) provide perceptual benefits over far-field HRTFs that enhance the plausibility of binaural rendering of nearby sound sources. However, to the best of our knowledge, no study has systematically investigated whether using near-field HRTFs actually provides a perceptually more plausible virtual acoustic environment. To assess this question, we conducted two experiments in a six-degrees-of-freedom multimodal augmented reality experience where participants had to compare non-individual anechoic binaural renderings based on either synthesized near-field HRTFs or intensity-scaled far-field HRTFs and judge which of the two rendering methods led to a more plausible representation. Participants controlled the virtual sound source position by moving a small handheld loudspeaker along a prescribed trajectory laterally and frontally near the head, which provided visual and proprioceptive cues in addition to the auditory cues. The results of both experiments show no evidence that near-field cues enhance the plausibility of non-individual binaural rendering of nearby anechoic sound sources in a dynamic multimodal virtual acoustic scene as examined in this study. These findings suggest that, at least in terms of plausibility, the additional effort of including near-field cues in binaural rendering may not always be worthwhile for virtual or augmented reality applications.
Highlights
Auditory distance perception is dominated by intensity cues [1, 2]
It is commonly believed that near-field head-related transfer functions (HRTFs) provide perceptual benefits over far-field HRTFs that enhance the plausibility of binaural rendering of nearby sound sources
The HRTF set was transformed to the spherical harmonics (SH) domain at a sufficiently high spatial order of N = 44, allowing artifact-free SH interpolation to obtain HRTFs for any desired direction, which was necessary in the present case for accurate HRTF synthesis
Summary
Auditory distance perception is dominated by intensity cues [1, 2]. In reverberant environments, distance judgments are aided by changes in the direct-to-reverberant energy ratio (DRR) [1, 2], and for far-away sources (more than 15 m), high-frequency attenuation provides additional spectral cues [1, 2]. It is crucial to know whether the additional computing effort of including near-field cues is worthwhile in terms of plausibility and overall reproduction quality, especially for complex realtime applications with limited computing resources, such as mobile AR applications with 6-DoF To close this gap and investigate whether near-field HRTFs provide a more plausible binaural reproduction of nearby sound sources than intensity-scaled far-field HRTFs, we performed two listening experiments in an anechoic 6-DoF VAE. In both experiments, participants controlled the position of a virtual sound source by moving a small handheld loudspeaker, which provided visual and proprioceptive cues in addition to the auditory cues and aided the application-oriented AR experience. To generalize the results of Experiment 1 to a more application-oriented setup, we used female speech as a test signal in Experiment 2
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