Physically based real-time auralization of interactive virtual environments

Over the last decades, Virtual Reality (VR) technology has emerged to be a powerful tool for a wide variety of applications covering conventional use, e.g., in science, design, medicine and engineering, as well as in more visionary applications such as the creation of virtual spaces that aim to act real. However, the high capabilities of today’s VR-systems are mostly limited to first-class visual rendering. In order to boost the range of applications, state-of-the-art systems aim to reproduce virtual environments as realistically as possible for the purpose of maximizing the user’s feeling of immersion, presence and acceptance. Such immersive systems deliver multiple sensory stimuli and provide an opportunity to act interactively, as reality is neither mono-modal nor static. Analogous to visualization, the auralization of virtual environments describes the simulation of sound propagation inside enclosures where methods of Geometrical Acoustics are mostly applied for a high-quality synthesis of aural stimuli that go along with a certain realistic behavior. Here, best results are achieved by combining deterministic methods for the computation of early specular sound reflections with stochastic approaches for the computation of the reverberant sound field. By adapting acceleration algorithms from Computer Graphics, current implementations can manage the computational load of moving sound sources around a moving receiver in real-time – even for complex but static architectural scenarios. In the course of this thesis, the design and implementation of the real-time room acoustics simulation software RAVEN will be described, which is a vital part of the implemented 3D sound-rendering system of RWTH Aachen University’s immersive VR-system. RAVEN relies on present-day knowledge of room acoustical simulation techniques and enables a physically accurate auralization of sound propagation in complex environments including important wave effects such as sound scattering, airborne sound insulation between rooms and sound diffraction. Despite this realistic sound field rendering, not only spatially distributed and freely movable sound sources and receivers are supported at runtime but also modifications and manipulations of the environment itself. All major features are evaluated by investigating both the overall accuracy of the room acoustics simulation and the performance of implemented algorithms, and possibilities for further simulation optimizations are identified by assessing empirical studies of subjects operating in immersive environments.