Perceptual factors contribute more than acoustical factors to sound localization abilities with virtual sources

Abstract

Human sound localization abilities rely on binaural and spectral cues. Spectral cues arise from interactions between the sound wave and the listener's body (head-related transfer function, HRTF). Large individual differences were reported in localization abilities, even in young normal-hearing adults. Several studies have attempted to determine whether localization abilities depend mostly on acoustical cues or on perceptual processes involved in the analysis of these cues. These studies have yielded inconsistent findings, which could result from methodological issues. In this study, we measured sound localization performance with normal and modified acoustical cues (i.e., with individual and non-individual HRTFs, respectively) in 20 naïve listeners. Test conditions were chosen to address most methodological issues from past studies. Procedural training was provided prior to sound localization tests. The results showed no direct relationship between behavioral results and an acoustical metrics (spectral-shape prominence of individual HRTFs). Despite uncertainties due to technical issues with the normalization of the HRTFs, large acoustical differences between individual and non-individual HRTFs appeared to be needed to produce behavioral effects. A subset of 15 listeners then trained in the sound localization task with individual HRTFs. Training included either visual correct-answer feedback (for the test group) or no feedback (for the control group), and was assumed to elicit perceptual learning for the test group only. Few listeners from the control group, but most listeners from the test group, showed significant training-induced learning. For the test group, learning was related to pre-training performance (i.e., the poorer the pre-training performance, the greater the learning amount) and was retained after 1 month. The results are interpreted as being in favor of a larger contribution of perceptual factors than of acoustical factors to sound localization abilities with virtual sources.

Experiments on localization accuracy with non-individual and individual HRTFs comparing static and dynamic reproduction methods

“…Regarding the accuracy of localizing in elevation no difference between individual and non-individual binaural stimuli could be found. In contrast to that, Andéol and colleagues found considerable differences in the low elevation region [11], [12], substantiating the fact that individual binaural stimuli yield a better localization accuracy in elevation than non-individual.…”

“…Møller and colleagues reported about more errors located in the median plane for dummy head HRTFs [11]. Additionally, Andéol and colleagues observed a higher rate of front-back-confusions also for individual HRTFs, but stated greater errors in elevation for the non-individual reproduction via headphones [12]. Dynamic reproduction, allowing for head movements, significantly improved spatial localization in terms of a reduced reversal error [9], [13]- [16].…”

The Impact of an Accurate Vertical Localization with HRTFs on Short Explorations of Immersive Virtual Reality Scenarios

“…Based on screening results, we defined a criterion which allowed to cluster users into good and bad localizers; we assumed that our personalization method provided reliable spectral cues in the acoustic domain for all users, thus confining the cause of poor/good localization performances in the non-acoustic domain. This hypothesis is strengthened by recent findings which identified a dominance of perceptual factors on acoustical factors for sound localization of virtual sound sources [3]. Accordingly, we focused our analysis on the impact that a perceptual characterization of user has the perceived quality of experience (QoE) for immersive and multimodal scenarios.…”

“…It is worthwhile to note that listening with HRTFs (both individual and even more non-individual) exhibits high variability in localization performance, in relation to both differences in acoustic factors due to listener anthropometry [15], and perceptual factors, i.e., the individual ability of encoding directional information [3,24]. Accordingly, it is very important to have a user characterization in terms of auditory abilities and HRTF usability, which should provide perceptually-relevant guidelines for a personalized design of full 3D spaces within an immersive and multimodal VR context.…”

SPHERE: A novel approach to 3D and active sound localization

“…Haber et al, 1993;. In addition, although sounds were delivered in 3D --hence, supposedly perceived in 3D space --the response was often limited to one dimension (e.g., in studies using a rotating dial to indicate angular sound position; Haber et al, 1993) or two dimensions (e.g., in studies using a remote display to indicate sound direction; Andéol et al, 2014).…”