Head Related Transfer Function And Acoustic Virtual Reality

This book covers all aspects of head-related transfer function (HRTF), from the fundamentals through to the latest applications, such as 3D sound systems. An introductory chapter defines HRTF, describes the coordinate system used in the book, and presents the most recent research achievements in the field. HRTF and sound localization in the horizontal and median planes are then explained, followed by discussion of individual differences in HRTF, solutions to this individuality (personalization of HRTF), and methods of sound image control for an arbitrary 3D direction, encompassing both classic theory and state of the art data. The relations between HRTF and sound image distance and between HRTF and speech intelligibility are fully explored, and measurement and signal processing methods for HRTF are examined in depth. Here, supplementary material is provided to enable readers to measure and analyze HRTF by themselves. In addition, some typical HRTF databases are compared. The final two chapters are devoted to the principles and applications of acoustic virtual reality. This clearly written book will be ideal for all who wish to learn about HRTF and how to use it in their research.

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 book systematically details the basic principles and applications of head-related transfer function (HRTF) and virtual auditory display (VAD), and reviews the latest developments in the field, especially those from the author’s own state-of-the-art research group. Head-Related Transfer Function and Virtual Auditory Display covers binaural hearing and the basic principles, experimental measurements, computation, physical characteristics analyses, filter design, and customization of HRTFs. It also details the principles and applications of VADs, including headphone and loudspeaker-based binaural reproduction, virtual reproduction of stereophonic and multi-channel surround sound, binaural room simulation, rendering systems for dynamic and real-time virtual auditory environments, psychoacoustic evaluation and validation of VADs, and a variety of applications of VADs. This guide provides all the necessary knowledge and latest results for researchers, graduate students, and engineers who work in the field of HRTF and VAD.

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.

Human sound localization helps to pay attention to spatially separated speakers using interaural level and time differences as well as angle-dependent monaural spectral cues. In a monophonic teleconference, for instance, it is much more difficult to distinguish between different speakers due to missing binaural cues. Spatial positioning of the speakers by means of binaural reproduction methods using head-related transfer functions (HRTFs) enhances speech comprehension. These HRTFs are influenced by the torso, head and ear geometry as they describe the propagation path of the sound from a source to the ear canal entrance. Through this geometry-dependency, the HRTF is directional and subject-dependent. To enable a sufficient reproduction, individual HRTFs should be used. However, it is tremendously difficult to measure these HRTFs. For this reason this thesis proposes approaches to adapt the HRTFs applying individual anthropometric dimensions of a user. Since localization at low frequencies is mainly influenced by the interaural time difference, two models to adapt this difference are developed and compared with existing models. Furthermore, two approaches to adapt the spectral cues at higher frequencies are studied, improved and compared. Although the localization performance with individualized HRTFs is slightly worse than with individual HRTFs, it is nevertheless still better than with non-individual HRTFs, taking into account the measurement effort.

The new realities are here. Virtual and Augmented realities and 360 video technologies are rapidly entering our homes and office spaces. Good quality audio has always been important to the user experience, but in the new realities, it is more than important, it’s essential. If the audio doesn’t work, the immersion of the experience fails and the cracks in the new reality start to show. This practical guide helps you navigate the challenges and pitfalls of designing audio for these new realities. This technology is different from anything we’ve seen before and requires an entirely new approach; this book will introduce the broad concepts you need to know before delving into the practical detail you need. Key Features This book covers audio for all types of new reality technology. At the moment, VR and 360 video are getting a lot of press, but in a few years we will be hearing a lot more about Augmented and Mixed reality technologies as well. A practical guide to creating, designing and implementing audio for this new technology by a leading sound design and implementation expert. Conceptual explanations address the new approaches necessary to designing effective audio for the new realities. Real-world examples and analysis of what does and does not work including detailed case study discussions.