Achieving a full 3D auditory experience with head-related transfer functions (HRTFs) is still one of the main challenges of spatial audio rendering. HRTFs capture the listener's acoustic effects and personal perception, allowing immersion in virtual reality (VR) applications. This paper aims to investigate the connection between listener sensitivity in vertical localization cues and experienced presence, spatial audio quality, and attention. Two VR experiments with head-mounted display (HMD) and animated visual avatar are proposed: (i) a screening test aiming to evaluate the participants' localization performance with HRTFs for a non-visible spatialized audio source, and (ii) a 2 minute free exploration of a VR scene with five audiovisual sources in a both non-spatialized (2D stereo panning) and spatialized (free-field HRTF rendering) listening conditions. The screening test allows a distinction between good and bad localizers. The second one shows that no biases are introduced in the quality of the experience (QoE) due to different audio rendering methods; more interestingly, good localizers perceive a lower audio latency and they are less involved in the visual aspects.

This paper presents two within-subjects studies (n=23) exploring how different combinations of visual and auditory feedback influence perceived realism, virtual self-perception and the experience of safety during walks on a virtual platform suspended over a canyon. In the first study, the frequency factor of the footstep sounds was altered and the visual appearance was changed between a newly built wooden bridge and an old bridge with a weaker structure and broken planks. In the second study, the sounds of creaking wood were added to the footstep sounds in half of the trails and compared against footsteps without creaking sounds. Moreover, the frequency factor of the frequency controls for footsteps was also manipulated between trails, but the visual appearance of the bridge was limited to the model of the old broken bridge.

In this paper we describe an experiment aiming to investigate the impact of auditory feedback in a virtual reality supermarket scenario. The participants were asked to read a shopping list and collect items one by one and place them into a shopping cart. Three conditions were presented randomly, where audio feedback was (1) absent, (2) had impact sounds for collisions including when grasping, (3) had impact sounds as well as continuous sounds when moving the products. The subjects experience of the simulation during the three experimental conditions were studied using a questionnaire where ratings on presence, body ownership, awareness of own movements, usability and enjoyment were collected. The results are presented and discussed.

An experiment investigated the subjective experiences of ownership and agency of a pair of virtual wings attached to a motion controlled avatar in an immersive virtual reality setup. A between groups comparison of two ways of controlling the movement of the wings and flight ability. One where the subjects achieved the wing motion and flight ability by using a hand-held video game controller and the other by moving the shoulder. Through four repetitions of a flight task with varying amounts of self-produced audio feedback (from the movement of the virtual limbs), the subjects evaluated their experienced embodiment of the wings on a body ownership and agency questionnaire. The results shows significant differences between the controllers in some of the questionnaire items and that adding self-produced sounds to the avatar, slightly changed the subjects evaluations.

This experiment aimed to investigate whether a user controlling a full body avatar via real time motion tracking in an immersive virtual reality setup, would estimate the weight of the virtual avatar differently if the footstep sounds are manipulated using three different audio filter settings. The visual appearance of the avatar was available in two sizes. The subjects performed six walks with each audio configuration active once over two ground types. After completing each walk, the participants were asked to estimate the weight of the virtual avatar and the suitability of the audio feedback. The results indicate that the filters amplifying the two lower center frequencies altered the subjects estimates of the weight of the avatar body towards being heavier than when compared with the filter with the higher center frequency. There were no significant differences between the weight estimates of the two groups using the different avatar bodies.

We describe two psychophysical experiments where we have quantified how much humans can unknowingly be redirected by auditory stimuli. The experiments use a two-alternative-forced-choice task. We tested 19 subjects in two different experiments: (E1) discrimination between virtual and physical rotation, and (E2) discrimination of path curvature. In experiment E1 subjects performed rotations with different gains, and then had to choose whether the auditory perceived rotation was smaller or greater than the physical rotation. In experiment E2 subjects estimate the path curvature when walking a curved path in the real world while the visual display shows a straight path in the virtual world. Our results show that users can be turned physically about 20% percent more or 12% less than the perceived virtual rotation, and users can be redirected on a circular arc while they believe they are walking straight.