Abstract
To reproduce realistic audio-visual scenarios in the laboratory, Ambisonics is often used to reproduce a sound field over loudspeakers and virtual reality (VR) glasses are used to present visual information. Both technologies have been shown to be suitable for research. However, the combination of both technologies, Ambisonics and VR glasses, might affect the spatial cues for auditory localization and thus, the localization percept. Here, we investigated how VR glasses affect the localization of virtual sound sources on the horizontal plane produced using either 1st-, 3rd-, 5th- or 11th-order Ambisonics with and without visual information. Results showed that with 1st-order Ambisonics the localization error is larger than with the higher orders, while the differences across the higher orders were small. The physical presence of the VR glasses without visual information increased the perceived lateralization of the auditory stimuli by on average about 2°, especially in the right hemisphere. Presenting visual information about the environment and potential sound sources did reduce this HMD-induced shift, however it could not fully compensate for it. While the localization performance itself was affected by the Ambisonics order, there was no interaction between the Ambisonics order and the effect of the HMD. Thus, the presence of VR glasses can alter acoustic localization when using Ambisonics sound reproduction, but visual information can compensate for most of the effects. As such, most use cases for VR will be unaffected by these shifts in the perceived location of the auditory stimuli.
Highlights
With the recent increase in quality and availability, head mounted virtual reality displays (HMDs) are regularly used in combination with virtual sound environments to create more realistic and immersive audio-visual experiments (e.g., Echevarria Sanchez et al, 2017; Kessling and Görne, 2018; Suárez et al, 2019)
Additional spherical harmonics can be included to improve the directional resolution of the reproduction (Gerzon, 1973; Bertet et al, 2013; Ahrens et al, 2020), referred to as higherorder Ambisonics (HOA)
Because a shift in the perceived location of the auditory stimulus is present, it will be important to take the effect of the HMD into account in experiments where the exact positioning of the stimuli is relevant, such as audio (-visual) localization experiments. These results only extend to the combination of the HMD with loudspeaker reproduced Ambisonics, headphone reproductions will not be shifted in the same way
Summary
With the recent increase in quality and availability, head mounted virtual reality displays (HMDs) are regularly used in combination with virtual sound environments to create more realistic and immersive audio-visual experiments (e.g., Echevarria Sanchez et al, 2017; Kessling and Görne, 2018; Suárez et al, 2019). For many studies, headphones might suffice as the playback method for this acoustic environment, there are many cases where loudspeaker playback might be preferred to preserve the participants own head-related transfer function or to be able to wear hearing aids or other ear-worn devices This is where potential problems can arise, as recent studies have shown that HMDs affect the acoustic signals (Genovese et al, 2018; Gupta et al, 2018; Ahrens et al, 2019). The added volume of the HMD modifies these cues, increasing the lateralization of the perceived location of stimuli (Gupta et al, 2018; Ahrens et al, 2019) Such changes in the perceived location of the sound could affect the perceived spatial location of a sound, and the integration of audio-visual stimuli.
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