Binaural technology for virtual reality

• Binauraltechnik für virtuelle Umgebungen

Lentz, Tobias; Vorländer, Michael (Thesis advisor)

Berlin : Logos-Verl. (2008)
Dissertation / PhD Thesis

In: Aachener Beiträge zur technischen Akustik 6
Page(s)/Article-Nr.: VI, 156 S. : Ill., graph. Darst.

Zugl.: Aachen, Techn. Hochsch., Diss., 2007

Abstract

The generation and use of non-intrusive artificial virtual environments is gaining more and more importance. Virtual environments are used in a variety of fields such as product design or evaluation of prototypes. Moreover they turned out to be very effective for the visualization of complex data sets. In the past, investigations were focused mainly on the visual reproduction technique to present geometrical data in a three-dimensional way (stereoscopic representation). However, the human perception consists not only of visual input but is based on a number of sensations and thus it would be worthwhile to create multi-modal and interactive virtual environments. In this thesis, first of all the techniques required to include the acoustic component into a virtual environment are described and assessed. Furthermore the implementation of a software system is described, which takes advantage of these techniques to create complex acoustical scenes in real time. It features spatially distributed sound sources which are utilized to create an environment that is as authentic as possible. The system is based on the binaural technology (binaural: "concerning both ears") and aims at reproducing a sound for the ears of the user that is equivalent to the sound in an original surrounding. It is essential to set up a sound field that is as exact as possible, to achieve a simulation with the highest degree of authenticity. 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. Therefore, the focus of the thesis is also put on the reproduction technology. In this context, an approach for dynamic crosstalk cancellations is presented, which enables a loudspeaker-based reproduction for binaural acoustical imaging instead of using headphones. Filters are necessary to ensure the required channel separation in a dynamic setting. These filters are calculated in real time on the basis of the given data concerning the position and measured transfer functions of the outer ear. Furthermore the integration of this spatial audio system into a Virtual Reality display system (five-sided CAVE-like environment) at the Center for Computing and Communication, RWTH Aachen University, is described and evaluated.