Binaural synthesis with head tracking is often used in spatial audio systems. The devices used for head tracking must provide data on the orientation of the listener’s head. These data need to be highly accurate, and they need to be provided as fast and as frequently as possible. Therefore, head-tracking devices need to be equipped with high-quality inertial measurement unit (IMU) sensors. Since IMUs readily include triaxial accelerometers, gyroscopes, and magnetometers, it is crucial that all of these sensors perform well, as the head orientation is calculated from all sensor outputs. This paper discusses the challenges encountered in the process of the performance assessment of IMUs through appropriate measurements. Three distinct hardware platforms were investigated: five IMU sensors either connected to Arduino-based embedded systems or being an integral part of one, five smartphones across a broad range of overall quality with integrated IMUs, and a commercial virtual reality unit that utilizes a headset with integrated IMUs. An innovative measurement method is presented and proposed for comparing the performance of sensors on all three platforms. The results of the measurements performed using the proposed method show that all three investigated platforms are adequate for the acquisition of the data required for calculating the orientation of a device as the input to the binaural synthesis process. Some limitations that have been observed during the measurements, regarding data acquisition and transfer, are discussed.

The use of audio systems that employ binaural synthesis with head tracking has become increasingly popular, particularly in virtual reality gaming systems. The binaural synthesis process uses the Head-Related Transfer Functions (HRTF) as an input required to assign the directions of arrival to sounds coming from virtual sound sources in the created virtual environments. Generic HRTFs are often used for this purpose to accommodate all potential listeners. The hypothesis of the research is that the use of individual HRTF in binaural synthesis instead of generic HRTF leads to improved accuracy and quality of virtual sound source localization, thus enhancing the user experience. A novel methodology is proposed that involves the use of dynamic virtual sound sources. In the experiments, the test participants were asked to determine the direction of a dynamic virtual sound source in both the horizontal and vertical planes using both generic and individual HRTFs. The gathered data are statistically analyzed, and the accuracy of localization is assessed with respect to the type of HRTF used. The individual HRTFs of the test participants are measured using a novel and efficient method that is accessible to a broad range of users.

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.