Physically Based Real Time Auralization Of Interactive Virtual Environments

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. 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 Virtual Reality 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

The use of non-intrusive virtual environments is gaining more and more importance but was focused mainly on addressing the visual sense. However, the human perception consists not only of visual input and thus it would be worthwhile to create multi-modal and interactive virtual environments. This thesis describes the techniques required to include the acoustic component into a virtual environment and furthermore the implementation of a software system, which takes advantage of these techniques to create complex acoustical scenes in real time. The system is based on the binaural technology. It features spatially distributed sound sources which are utilized to create an environment that is as authentic as possible. This comprises a description of the source, including its relevant angle-, distance- and time- dependent radiation, the sound distribution in the virtual scene (room acoustics), the perception-related consideration of all sound field components, as well as the exact reproduction of the artificial sound at the ears of the user. The focus of this thesis is put on the reproduction technology. In this context, an approach for dynamic crosstalk cancellation is presented, which enables a loudspeaker-based reproduction. The required filters are processed in real time on the basis of the position data and measured transfer functions of the outer ear. Furthermore the integration of this spatial audio system into a five-sided Virtual Reality display system is described and evaluated.

This open access book tackles the design of 3D spatial interactions in an audio-centered and audio-first perspective, providing the fundamental notions related to the creation and evaluation of immersive sonic experiences. The key elements that enhance the sensation of place in a virtual environment (VE) are: Immersive audio: the computational aspects of the acoustical-space properties of Virutal Reality (VR) technologies Sonic interaction: the human-computer interplay through auditory feedback in VE VR systems: naturally support multimodal integration, impacting different application domains Sonic Interactions in Virtual Environments will feature state-of-the-art research on real-time auralization, sonic interaction design in VR, quality of the experience in multimodal scenarios, and applications. Contributors and editors include interdisciplinary experts from the fields of computer science, engineering, acoustics, psychology, design, humanities, and beyond. Their mission is to shape an emerging new field of study at the intersection of sonic interaction design and immersive media, embracing an archipelago of existing research spread in different audio communities and to increase among the VR communities, researchers, and practitioners, the awareness of the importance of sonic elements when designing immersive environments.

This book gives a broad overview of research on sound simulation driven by a variety of applications. Vibrating objects produce sound, which then propagates through a medium such as air or water before finally being heard by a listener. As a crucial sensory channel, sound plays a vital role in many applications. There is a well-established research community in acoustics that has studied the problems related to sound simulation for six decades. Some of the earliest work was motivated by the design of concert halls, theaters, or lecture rooms with good acoustic characteristics. These problems also have been investigated in other applications, including noise control and sound design for urban planning, building construction, and automotive applications. Moreover, plausible or realistic sound effects can improve the sense of presence in a virtual environment or a game. In these applications, sound can provide important clues such as source directionality and spatial size. The book first surveys various sound synthesis methods, including harmonic synthesis, texture synthesis, spectral analysis, and physics-based synthesis. Next, it provides an overview of sound propagation techniques, including wave-based methods, geometric-based methods, and hybrid methods. The book also summarizes various techniques for sound rendering. Finally, it surveys some recent trends, including the use of machine learning methods to accelerate sound simulation and the use of sound simulation techniques for other applications such as speech recognition, source localization, and computer-aided design.

In consideration of the remarkable intensity of research in the field of Virtual Acoustics, including different areas such as sound field analysis and synthesis, spatial audio technologies, and room acoustical modeling and auralization, it seemed about time to organize a second international symposium following the model of the first EAA Auralization Symposium initiated in 2009 by the acoustics group of the former Helsinki University of Technology (now Aalto University). Additionally, research communities which are focused on different approaches to sound field synthesis such as Ambisonics or Wave Field Synthesis have, in the meantime, moved closer together by using increasingly consistent theoretical frameworks. Finally, the quality of virtual acoustic environments is often considered as a result of all processing stages mentioned above, increasing the need for discussions on consistent strategies for evaluation. Thus, it seemed appropriate to integrate two of the most relevant communities, i.e. to combine the 2nd International Auralization Symposium with the 5th International Symposium on Ambisonics and Spherical Acoustics. The Symposia on Ambisonics, initiated in 2009 by the Institute of Electronic Music and Acoustics of the University of Music and Performing Arts in Graz, were traditionally dedicated to problems of spherical sound field analysis and re-synthesis, strategies for the exchange of ambisonics-encoded audio material, and – more than other conferences in this area – the artistic application of spatial audio systems. This publication contains the official conference proceedings. It includes 29 manuscripts which have passed a 3-stage peer-review with a board of about 70 international reviewers involved in the process. Each contribution has already been published individually with a unique DOI on the DepositOnce digital repository of TU Berlin. Some conference contributions have been recommended for resubmission to Acta Acustica united with Acustica, to possibly appear in a Special Issue on Virtual Acoustics in late 2014. These are not published in this collection.

This book is a printed edition of the Special Issue "Noise and Vibration Control in the Built Environment" that was published in Applied Sciences

This thesis describes the development of the real-time convolution system (RTCS) for a little-studied talker/listener in virtual acoustic environments. We include descriptions of the high-resolution directivity measurements of human speech, the RTCS system components, the measurement and characterization of oral-binaural room impulse responses (OBRIRs) for a variety of acoustic environments, and the compensation filter necessary for its validity. In addition to incorporating the high-resolution directivity measurements, this RTCS improved on that developed by Cabrera et al. [1] through the derivation and inclusion of the compensation filter. Objective measures in the time- and frequency-domains, as well as subjective measures, were developed to assess the validity of the RTCS. The utility of the RTCS is demonstrated in the study on vocal effort, and the results of an initial investigation into the vocal effort data are presented.

Auralization is the technique of creation and reproduction of sound on the basis of computer data. With this tool it is possible to predict the character of sound signals which are generated at the source and modified by reinforcement, propagation and transmission in systems such as rooms, buildings, vehicles or other technical devices. This book is organized as a comprehensive collection of the basics of sound and vibration, acoustic modelling, simulation, signal processing and audio reproduction. With some mathematical prerequisites, the readers will be able to follow the main strategy of auralization easily and work out their own implementations of auralization in various fields of application in architectural acoustics, acoustic engineering, sound design and virtual reality. For readers interested in basic research, the technique of auralization may be useful to create sound stimuli for specific investigations in linguistic, medical, neurological and psychological research, and in the field of human-machine interaction.

This work discusses methods for efficient audio processing with finite impulse response (FIR) filters. Such filters are widely used for high-quality acoustic signal processing, e.g. for headphone or loudspeaker equalization, in binaural synthesis, in spatial sound reproduction techniques and for the auralization of reverberant environments. This work focuses on real-time applications, where the audio processing is subject to minimal delays (latencies). Different fast convolution concepts (transform-based, interpolation-based and number-theoretic), which are used to implement FIR filters efficiently, are examined regarding their applicability in real-time. These fast, elementary techniques can be further improved by the concept of partitioned convolution. This work introduces a classification and a general framework for partitioned convolution algorithms and analyzes the algorithmic classes which are relevant for real-time filtering: Elementary concepts which do not partition the filter impulse response (e.g. regular Overlap-Add and Overlap-Save convolution) and advanced techniques, which partition filters uniformly and non-uniformly. The algorithms are thereby regarded in their analytic complexity, their performance on target hardware, the optimal choice of parameters, assemblies of multiple filters, multi-channel processing and the exchange of filter impulse responses without audible artifacts. Suitable convolution techniques are identified for different types of audio applications, ranging from resource-aware auralizations on mobile devices to extensive room acoustics audio rendering using dedicated multi-processor systems.