DSP Implementation of Head Related Binaural Sound Reproduction

A Project by ... Markus Noisternig, noisternig [at] iem.at Piotr Majdak, piotr [at] majdak.com (C) 2002 IEM, Graz Contributors Alois Sontacchi, sontacchi [at] iem.at Robert Höldrich, hoeldrich [at] iem.at Contact details Institute of Electronic Music and Acoustics (IEM) Inffeldgasse 10/3, 8010 Graz, Austria email :: noisternig [at] iem.at phone :: +43.316.389.3681 mobile:: +43.664.5301110

Abstract

Sound source spatialization in virtual acoustic environments requires to filter the source signals with head related transfer functions (HRTFs) to create the left and right ear signals. The HRTFs capture the diffraction of a sound wave from a certain direction of arrival caused by the torso, head, shoulders and pinnae of the listener. Consequently they show a great person-to-person variability. The use of nonindividualized transfer functions yields a degradation of human localization accuracy. In real world environments humans are able to improve their localization accuracy by performing small unconscious head movements.

To benefit from this in binaural audio systems head tracking has to be incorporated. This yields the problem of high-quality time-varying interpolation between different HRIRs. The proposed method solves this problem with a virtual Ambisonic approach which results in time-invariant filters. The influence of head position is taken into account with a computationally cheap time-variant rotation matrix in Amb isonics domain.

A mathematical model to simulate humans sound localization performance using HRIR based binaural reproduction systems is presented. To evaluate the significance of the proposed mathematical model, extensive listening tests have been carried out.
Further, the optimised algorithm is implemented on a DSP to estimate the feasibility to develop a consumer product.

Further Information

• ambi_bin: A Library for Real-Time 3D Binaural Sound Reproduction in Pure Data (PD) [Link to Project Page]
• M. Noisternig, P. Majdak"Implementation kopfpositionsbezogener Binauraltechnik", Master Thesis, Institute of Electronic Music and Acoustics, University of Music and dramatic Arts, Graz, Austria, 2002 [PDF] (German only!).
• A. Sontacchi, M. Noisternig, P. Majdak, and R. Hoeldrich, "Subjective Validation of Perception Properties in Binaural Sound Reproduction Systems", Proc. Int. Conf. Audio Eng. Soc., St. Petersburg, Russia, June, 2002 [PDF]
• A. Sontacchi, M. Noisternig, P. Majdak, and R. Hoeldrich, "An Objective Model of Localisation in Binaural Sound Reproduction Systems", Proc. Int. Conf. Audio Eng. Soc., St. Petersburg, Russia, June, 2002 [PDF]