Virtual sound source perception challenges of binaural audio systems with head-tracking

With the recent leaps in spatial audio technology, the use of binaural head-tracking for spatial audio can revolutionize the way how music and audio are experienced. Moreover, to research noise-related perception in laboratories, binaural head-tracking is frequently used as an audio reproduction system. Although this technology is getting significantly better in recent years, signal processing of binaural audio is often experiencing problems such as non-adequate sound source externalization and unacceptably high values of system response time since it influences the usability of the technology at fast head rotation. In this paper, the results of an experiment are presented, in which test subjects are determining the direction of a virtual sound source in the horizontal plane with multiple parameter changes. The experiment is done in a controlled environment in a listening room with known acoustical properties. Parameter variation includes: hardware head-tracker variation (commercial one and head-tracker based on simple embedded system), various software solutions for real-time binaural synthesis, and variation in the used Head-Related Transfer Functions. The problem of externalization of a virtual sound source via headphones is discussed, and possible solutions to the problem are given. Results of the experiment and recorded data are presented.