Hearing in virtual spaces - How real does virtual reality sound?
How people perceive sounds is a well understood process. A less researched area is the differences between sound perception in real and virtual environments, especially when it comes to the perception of distance. With the increasingly frequent use of virtual reality (VR) in scientific experiments, it has become even more important to better understand the specifics of hearing in virtual environments. Researchers at IfADo and Ruhr-Universität Bochum have now taken on this task as part of the AUDICTIVE program and recently published their findings.

Hearing is not just about grasping and processing the content of what we hear. The brain also tries to determine the origin of the sound - from which direction it is coming and how far away the source is. This is done by interpreting various characteristics of the sound. Of course, its volume plays a role, but the reverberation and tone as well as delays in when it reaches the left and right ear are also decisive factors. These characteristics can also be simulated in virtual environments to create a plausible auditory impression. However, the extent to which this resembles sound perception in a comparable real-life situation is still largely unexplored.
Correctly assess the distance of sounds: Are simulated sounds perceived comparably?
The researchers investigated this in an experiment in which they placed three loudspeakers two, four and eight meters away from a test subject. The test subjects were then played sounds - both from the loudspeakers and simulated sounds corresponding to the loudspeaker position via headphones. In most cases, the sounds were played from the loudspeaker four meters away. However, as soon as the position changed, the test subject was asked to indicate whether the sound was coming from further in front or further behind. In addition, the researchers adapted the same experiment so that the sounds were equally loud when they reached the subject's ears, regardless of their distance. This meant that the test subjects could not rely solely on the volume of the sound during the task.
However, the researchers not only investigated whether the test subjects were able to correctly identify the source of the sounds, but also what was happening in their heads. Using an EEG, they are able to visualize the electrical potentials during processing in the brain. As these potentials also look similar when perceived similarly, they can provide a further indication of whether the changes in position of the sounds in real and virtual environments are actually processed in the same or different ways.
Good news for experiments: sounds in VR are comparable, at a consistent volume
The study comes to the conclusion that the changes in position of sounds in the virtual and real environment are perceived in a comparable way and processed similarly in the brain. Only when the volume was adjusted in VR and therefore could not provide a reliable clue about the distance did the test subjects have difficulties with correct classification. Taking this limitation into account, however, the study shows that experiments in VR can be a good alternative that offers more freedom in the environments investigated and at the same time reduces the effort and costs of the experiments.
AUDICTIVE SPP2236
The study is part of the AUDICTIVE SPP2236 priority program, which is funded by the German Research Foundation (DFG). As part of the project, researchers from various research institutions and three disciplines (acoustics, cognitive psychology and VR/computer science) are investigating the perception and processing of sounds in virtual environments. More information about the project and other publications can be found on the project website: https://www.spp2236-audictive.de