Effects of virtual acoustics on dynamic auditory distance perception

Sound propagation encompasses various acoustic phenomena including reverberation. Current virtual acoustic methods, ranging from parametric filters to physically-accurate solvers, can simulate reverberation with varying degrees of fidelity. We investigate the effects of reverberant sounds generated using different propagation algorithms on acoustic distance perception, i.e., how faraway humans perceive a sound source. In particular, we evaluate two classes of methods for real-time sound propagation in dynamic scenes based on parametric filters and ray tracing. Our study shows that the more accurate method shows less distance compression as compared to the approximate, filter-based method. This suggests that accurate reverberation in VR results in a better reproduction of acoustic distances. We also quantify the levels of distance compression introduced by different propagation methods in a virtual environment.Comment: 8 Pages, 7 figure

Redefining A in RGBA: Towards a Standard for Graphical 3D Printing

Advances in multimaterial 3D printing have the potential to reproduce various visual appearance attributes of an object in addition to its shape. Since many existing 3D file formats encode color and translucency by RGBA textures mapped to 3D shapes, RGBA information is particularly important for practical applications. In contrast to color (encoded by RGB), which is specified by the object's reflectance, selected viewing conditions and a standard observer, translucency (encoded by A) is neither linked to any measurable physical nor perceptual quantity. Thus, reproducing translucency encoded by A is open for interpretation. In this paper, we propose a rigorous definition for A suitable for use in graphical 3D printing, which is independent of the 3D printing hardware and software, and which links both optical material properties and perceptual uniformity for human observers. By deriving our definition from the absorption and scattering coefficients of virtual homogeneous reference materials with an isotropic phase function, we achieve two important properties. First, a simple adjustment of A is possible, which preserves the translucency appearance if an object is re-scaled for printing. Second, determining the value of A for a real (potentially non-homogeneous) material, can be achieved by minimizing a distance function between light transport measurements of this material and simulated measurements of the reference materials. Such measurements can be conducted by commercial spectrophotometers used in graphic arts. Finally, we conduct visual experiments employing the method of constant stimuli, and derive from them an embedding of A into a nearly perceptually uniform scale of translucency for the reference materials.Comment: 20 pages (incl. appendices), 20 figures. Version with higher quality images: https://cloud-ext.igd.fraunhofer.de/s/pAMH67XjstaNcrF (main article) and https://cloud-ext.igd.fraunhofer.de/s/4rR5bH3FMfNsS5q (appendix). Supplemental material including code: https://cloud-ext.igd.fraunhofer.de/s/9BrZaj5Uh5d0cOU/downloa

Moving Sounds Enhance the Visually-Induced Self-Motion Illusion (Circular Vection) in Virtual Reality

While rotating visual and auditory stimuli have long been known to elicit self-motion illusions (“circular vection”), audiovisual interactions have hardly been investigated. Here, two experiments investigated whether visually induced circular vection can be enhanced by concurrently rotating auditory cues that match visual landmarks (e.g., a fountain sound). Participants sat behind a curved projection screen displaying rotating panoramic renderings of a market place. Apart from a no-sound condition, headphone-based auditory stimuli consisted of mono sound, ambient sound, or low-/high-spatial resolution auralizations using generic head-related transfer functions (HRTFs). While merely adding nonrotating (mono or ambient) sound showed no effects, moving sound stimuli facilitated both vection and presence in the virtual environment. This spatialization benefit was maximal for a medium (20 degrees × 15 degrees) FOV, reduced for a larger (54 degrees × 45 degrees) FOV and unexpectedly absent for the smallest (10 degrees × 7.5 degrees) FOV. Increasing auralization spatial fidelity (from low, comparable to five-channel home theatre systems, to high, 5 degree resolution) provided no further benefit, suggesting a ceiling effect. In conclusion, both self-motion perception and presence can benefit from adding moving auditory stimuli. This has important implications both for multimodal cue integration theories and the applied challenge of building affordable yet effective motion simulators

Seamless and Secure VR: Adapting and Evaluating Established Authentication Systems for Virtual Reality

Virtual reality (VR) headsets are enabling a wide range of new opportunities for the user. For example, in the near future users may be able to visit virtual shopping malls and virtually join international conferences. These and many other scenarios pose new questions with regards to privacy and security, in particular authentication of users within the virtual environment. As a first step towards seamless VR authentication, this paper investigates the direct transfer of well-established concepts (PIN, Android unlock patterns) into VR. In a pilot study (N = 5) and a lab study (N = 25), we adapted existing mechanisms and evaluated their usability and security for VR. The results indicate that both PINs and patterns are well suited for authentication in VR. We found that the usability of both methods matched the performance known from the physical world. In addition, the private visual channel makes authentication harder to observe, indicating that authentication in VR using traditional concepts already achieves a good balance in the trade-off between usability and security. The paper contributes to a better understanding of authentication within VR environments, by providing the first investigation of established authentication methods within VR, and presents the base layer for the design of future authentication schemes, which are used in VR environments only