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Figure 3. Virtual reconstruction of the historic jazz festival in the Casino of Montreux (Switzerland). Available at bit.ly/2vnS8BX.
reproduction. The mathematical concept for ambisonics is based on spherical harmonics (SH), which is an orthogonal functional base that serves as a solution of the wave equation in spherical coordinates. This solution enables plane-wave decomposition of the virtual sound, and from this the volt- ages driving the loudspeaker are calculated so that the array creates the exact sound arriving from the correct direction. Other loudspeaker-based techniques are vector-base ampli- tude panning and wave field synthesis, both employing channels in various orders or numbers. More information can be found in Pulkki (1997) and Berkhout (1988).
Applications: Here We Go!
The main feature of VA is the separation of the chain of sound production to sound propagation to sound perception into its elements. Once this is done, it is then possible to do free com- binations of sound events in various virtual environments for either indoor or outdoor scenes. There are numerous appli- cations of VA environments in research, in sound design, in noise control, and in acoustic archeology, just to name a few areas. AVR is a meeting point for several technical areas of the Acoustical Society of America!
Revival of Historic Places: Architectural and Computational Acoustics Meet Signal Processing
The Casino in Montreux
The Casino in Montreux (Switzerland) at Lake Geneva was a unique venue that hosted the most important jazz festival in Europe. The Montreux Jazz Festival, started in 1967, high- lighted the crème de la crème in jazz.
The historic casino building, however, was destroyed in a fire in 1971 during a concert by Frank Zappa and the Mothers of Invention. An interesting side note is that this disaster was referred to by the rock band Deep Purple with “Smoke on the Water” (see bit.ly/2Q8qMbg). From then on, of course, the famous Montreux Jazz Festival had to find another venue. Still, audience and musicians did feel nostalgic about the loss of atmosphere and passion. But there is help: virtual reality!
Imagine that the legendary casino building in Montreux is revived. In fact, Schröder et al. (2015) created a virtual Montreux Casino experience covering the years 1967–1971. This was presented to the audience during the Montreux Jazz Festival in 2014 (Figure 3).
San Juan de Baños
In a similar way, Pedrero et al. (2013) presented a reconstruc- tion of an eleventh century church in Spain. The aim was to study “Mozarabic chant” (Asensio Palacios, 2004), which was used when Spain was under Arabic control and decoupled from the Catholic center in Rome (see bit.ly/2XayN0Y). The church is San Juan de Baños in Baños de Cerrato (Castilla y León, Spain), near the city of Valladolid (Figure 4). In the eleventh century, the rites and the music in the ceremony were created in an isolated region, which is very interest- ing for research on culture and music history. Accordingly, various settings found in historic documents and paintings were constructed in VR and the acoustic effect on the sing- ing voices was studied. This included speculations about the existence of heavy curtains and their influence on the sound
Figure 4. The church San Juan de Baños in Spain in virtual reconstruction of the situation in the eleventh century. See video at bit.ly/2rIWuSp.
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