Jyväskylä Sinfonia is a small symphony orchestra with 38 musicians, conducted by Ville Matvejeff. The orchestra performs 1–2 times per week, and its repertoire consists mostly of baroque, symphonic, and contemporary music. The rehearsal hall used by Jyväskylä Sinfonia is located on the top floor of a shopping centre (Fig. 1), originally built in 1938. Prior to being used as a rehearsal hall, the attic space had originally been designed as a tennis hall.
The inclined walls of the room were lined with mineral wool, and the ceiling was otherwise covered with convex surfaces, probably designed to act as diffusers. Vertical plates backed with mineral wool had also been suspended from the ceiling (Fig. 2). Musicians from the orchestra reported that the rehearsal hall was too dry for symphonic music. The hall had also been reported to be very loud, leading to occupational health issues within the orchestra. There had apparently been an attempt to control the loudness of the space by adding a substantial amount of mineral wool, which had the effect of reducing the reverberation time to an unacceptable level.
Acoustic criteria for rehearsal rooms are presented in the Norwegian standard NS 8178:2014. According to the standard, a rehearsal hall for a symphony orchestra should have a net volume of at least 1800 m³. However, the space in question consisted of a 264 m² rectangular rehearsal room with an arched ceiling and a volume of 1100 m³. For this smaller volume, the standard gives a recommended reverberation time of 0.9–1.4 seconds for acoustically loud music.
Considering the dimensions of the room and the opinions of the musicians, an acoustic renovation was designed for the room by AINS Group, focused on increasing the reverberation time of the space without increasing the loudness.
