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Figure 6. This is a quite uncommon environment, but, hopefully, the listener (with head-mounted display sitting in an Ambisonics loudspeaker array) is immersed in the virtual scene.
to immersion as a personal experience, which usually occurs only in virtual environments and at most arises in other media when a human strongly identifies with the nature of the presented content.
No standard methodology yet exists for measuring immer- sion. In a study linking psychology and acoustics, Colsman et al. (2017) created a catalog with questions in four catego- ries, where room perception, source perception, attention (engagement), and causality are separate components of the feeling of presence in the environment surrounding us. Using this method, VR systems can be assessed if the sources, the rendering algorithms, and the audio reproduction are suf- ficient for the application.
Final Remarks
More studies in the field of VR are increasingly important because virtual environments offer ground-breaking oppor- tunities for advances in sound assessment, psychoacoustic research, and hearing diagnosis and rehabilitation, just to name a few examples. The ability to process dynamic acoustic situations is an essential component for communication and orientation in everyday life. Nevertheless, the test methods in current practice are far from being under realistic conditions because of too-simple acoustic stimuli.
AVR is the solution because it can incorporate any scene condition with sources and sound propagation features in the environment. The main research direction in AVR is
focused on overcoming the constraints of (1) the number of objects in the scene (e.g., maximal number of sources) and (2) the number of reflecting or diffracting objects that can be handled in real time.
AVR can be used in consulting and acoustics in practice as well! Research and development today is unthinkable without computer tools. In acoustics, computer data as well as mea- surement data are analyzed regarding the criteria of interest, such as noise levels, speech quality, reverberation times, and source identification. Displaying the data in diagrams, tables, or color maps helps to interpret the acoustic situation. This is a solid basis, for example, in acoustic consulting. When it comes to communication with naive clients, local authorities, or the public, drawbacks are a lack of knowledge about acoustics and, hence, there is a risk of misunderstanding. Examples and case studies may help, but VR does a much better job. The acoustic information is now presented through headphones or loud- speakers. It is remarkable how immediate and unambiguous the relevant information is now conveyed to the listener!
Audiovisual Examples
Virtual acoustics at ITA RWTH Aachen University:
bit.ly/36ZIqUw.
Urban park and congress center: bit.ly/33L4foW. Aircraft noise: bit.ly/33KzgcB.
Interactive scene in a park: bit.ly/2peKdnE. Experience of reverberation: bit.ly/2X8CxQs. Interaction with virtual humans: bit.ly/373l0hd.
Acknowledgments
I thank Arthur Popper for his very helpful comments and suggestions on the manuscript. Also, big thanks go to the past and present members of the Virtual Reality Group at the Institute of Technical Acoustics, RWTH Aachen Univer- sity, for working together so nicely and for creating the audio and video examples: Lukas Aspöck, Michael Kohnen, Tobias Lentz, Imran Muhammad, Sönke Pelzer, Dirk Schröder, Jonas Stienen, and Frank Wefers. The work by Michael Vorländer and his group was mainly supported by the Deutsche Forschungsgemeinschaft.
References
Ackermann, D., Böhm, C., Brinkmann, F., and Weinzierl, S. (2019). The acoustical effect of musicians' movements during musical performances.
Acta Acustica united with Acustica 105(2), 356-367. https://doi.org/10.3813/AAA.919319.
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