This study uses a mixed between- and within-subjects test design to evaluate the influence of interactive formats on the quality of binaurally rendered 360° spatial audio content. Focusing on ecological validity using real-world recordings of 60 s duration, three independent groups of subjects () were exposed to three formats: audio only (A), audio with 2D visuals (A2DV), and audio with head-mounted display (AHMD) visuals. Within each interactive format, two sessions were conducted to evaluate degraded audio conditions: bit-rate and Ambisonics order. Our results show a statistically significant effect (p < .05) of format only on spatial audio quality ratings for Ambisonics order. Exploration data analysis shows that format A yields little variability in exploration, while formats A2DV and AHMD yield broader viewing distribution of 360° content. The results imply audio quality factors can be optimized depending on the interactive format.

Research into multi-modal perception, human cog-nition, behavior, and attention can benefit from high-fidelity content that may recreate real-life-like scenes when rendered on head-mounted displays. Moreover, aspects of audiovisual perception, cognitive processes, and behavior may complement questionnaire-based Quality of Experience (QoE) evaluation of interactive virtual environments. Currently, there is a lack of high-quality open-source audiovisual databases that can be used to evaluate such aspects or systems capable of reproducing high-quality content. With this paper, we provide a publicly available audiovisual database consisting of twelve scenes capturing real-life nature and urban environments with a video resolution of 7680×3840 at 60 frames-per-second and with 4th-order Ambison-ics audio. These 360° video sequences, with an average duration of 60 seconds, represent real-life settings for systematically evaluating various dimensions of uni-/multi-modal perception, cognition, behavior, and QoE. The paper provides details of the scene requirements, recording approach, and scene descriptions. The database provides high-quality reference material with a balanced focus on auditory and visual sensory information. The database will be continuously updated with additional scenes and further metadata such as human ratings and saliency information.

Many quality evaluation methods are used to assess uni-modal audio or video content without considering perceptual, cognitive, and interactive aspects present in virtual reality (VR) settings. Consequently, little is known regarding the repercussions of the employed evaluation method, content, and subject behavior on the quality ratings in VR. This mixed between- and within-subjects study uses four subjective audio quality evaluation methods (viz. multiple-stimulus with and without reference for direct scaling, and rank-order elimination and pairwise comparison for indirect scaling) to investigate the contributing factors present in multi-modal 6-DoF VR on quality ratings of real-time audio rendering. For each between-subjects employed method, two sets of conditions in five VR scenes were evaluated within-subjects. The conditions targeted relevant attributes for binaural audio reproduction using scenes with various amounts of user interactivity. Our results show all referenceless methods produce similar results using both condition sets. However, rank-order elimination proved to be the fastest method, required the least amount of repetitive motion, and yielded the highest discrimination between spatial conditions. Scene complexity was found to be a main effect within results, with behavioral and task load index results implying more complex scenes and interactive aspects of 6-DoF VR can impede quality judgments.

Virtual reality (VR) technology enables and requires new ways of user experience testing in immersive environments. For various aspects of user experience, objective assessment of the cognitive load can be a useful parameter. With eye-tracking becoming a more widespread feature of current VR headsets, pupillometry is an appealing option to unobtrusively measure cognitive load during a VR experience. This paper shows that pupil size measured by an off-the-shelf VR headset with an integrated eye tracker positively correlates with the self-reported cognitive load during a standard n-back task adapted to a VR environment. To overcome the need for steady scene-lighting conditions, we present a method to correct for the light-induced pupil size changes, otherwise masking the cognitive load effects. Our results show that a commercially available VR headset with eye tracking can be used to measure the cognitive load in unpredictable lighting conditions without additional hardware.

This paper proposes a new method for evaluating real-time binaural reproduction systems by means of a wayfinding task in six degrees of freedom. Participants physically walk to sound objects in a virtual reality created by a head-mounted display and binaural audio. We show how the localization accuracy of spatial audio rendering is reflected by objective measures of the participants' behavior. The method allows for comparative evaluation of different rendering systems as well as the subjective assessment of the quality of experience.

Most research on multisensory processing focuses on impoverished stimuli and simple tasks. In consequence, very little is known about the sensory contributions in the perception of real environments. Here, we presented 23 participants with paired comparison tasks, where natural scenes were discriminated in three perceptually meaningful attributes: movement, openness, and noisiness. The goal was to assess the auditory and visual modality contributions in scene discrimination with short (≤500ms) natural scene exposures. The scenes were reproduced in an immersive audiovisual environment with 3D sound and surrounding visuals. Movement and openness were found to be mainly visual attributes with some input from auditory information. In some scenes, the auditory system was able to derive information about movement and openness that was comparable with audiovisual condition already after 500ms stimulation. Noisiness was mainly auditory, but visual information was found to have a facilitatory role in a few scenes. The sensory weights were highly imbalanced in favor of the stronger modality, but the weaker modality was able to affect the bimodal estimate in some scenes.