Room Acoustic Projects in Scandinavia

Transcription

1 Room Acoustic Projects in Scandinavia Tor Halmrast 1) Statsbygg, pb. 8106, Dep. NO-0032 OSLO, Norway, 2) University of Oslo, Dep. Of Musicology, OSLO, Norway The paper is a continuation of the authors paper Projects in Scandinavia for the IoA conference in Copenhagen 2006, and will include updated info on some contemporary Concert Halls project, including the refurbishment of the University Aula in Oslo, with its listed acoustics and large paintings of Edvard Munch.. 1 Introduction Statsbygg is the Norwegian Directorate of Public Construction, and as so, responsible for most of the building projects for state owned buildings: New Oslo Opera, Nationaltheatret, Universities and University Colleges, Musikkhøgskolen and the excellent chamber music hall: The University Aula in Oslo. In addition, Statsbygg/Acoustics has served as client advisor in acoustics for several other building projects including concert halls and theatres. This paper is a follow up of the paper Some projects in Scandinavia given at the Institute of Acoustics (IoA) conference in Copenhagen in University Aula, Oslo The Aula of the University is situated in the very centre of Oslo. Just across the main street, Karl Johans gt you find Nationaltheatret, and very close is both the Royal Castle and the Government. The main part of this downtown university was built around 1880, and the Aula was built At the opening in 1916 the room had no painting, and loose chairs for banquets. (picture right)

2 2.1 Edvard Munch in the Aula There was a long, hard and troublesome competition for the decoration of the Aula. Edvard Munch finally won, with the Sun (app 4.5 x 7.9 m) as the middle focus and Frieze of Life around the walls. The paintings were donated to the University in 1919 and covers 220m 2 of the three main walls of the hall. Behind the paintings and the marble cladding there is a brick outer wall. The paintings were remounted in 1926 and cleaned in The Aula during the war After the German invasion in 1940, there came a whisper that the Germans planned to take over the Aula very soon. The University and the leader of the National Museum had just one day to take down all the paintings and secure them in the silver mines in Kongsberg. Due to the short notice, the paintings had to be cut from the frames, and rolled together. Some damage was done and edge parts of the motifs were lost. The quick and hazardous operation proved necessary, also because the Aula burnt at the end of the German occupation (in 1944). After the war, the paintings were reinstalled, mounted on masonit plates. 2.3 The Aula as concert hall The Aula was the home of the Oslo Philharmonic up the opening of Oslo Concert House in 1977, and is well known for it s excellent acoustics, especially for recitals and chamber music/chamber orchestra. No well known Norwegian musician has succeeded without having his/hers debut concert in the University Aula. Before the renovation (-2011) Statsbygg/Acoustics proposed that the acoustics of the Aula should be considered listed, not just the interior and the paintings. ( Listed in the meaning that it should be preserved, even if 100 acousticians and musicians should vote for a change )

3 2.4 The refurbishment All the paintings were removed The absorption of the paintings were measured before/after the renovation: The Stage Floor was studied before it was all taken away and a new stage was built, somewhat bigger, but the main issue was to keep the same thickness/weight/resonances. A stage lift was needed for transportation, and this was first planned to be on the right side of the stage (seen from the audience), but this was not allowed for acoustical reasons, as this is a common area for double bass (and sometimes celli) which need the original support from a resonating floor. The discussion on how to to follow this acoustic need where not as straightforward, as the room under the chosen position (to the left, in front of the stage, the normal position for violin1, which do not need floor support) leads down to the only real wardrobe in the building, which had a listed design. This listing was decided to be less important than the acoustics. The Audience Floor construction was investigated, and it was important that the new floor, with heating ducts, should not change the acoustics of the hall. The glass-ceiling was, for security reasons made somewhat heavier after the renovation, and in the loft above the roof was closed, so no actual daylight (nor traffic noise) reaches the Aula.

4 m2 sabine The sofas were neatly restored, with the original type of textile: The chairs were measured in the lab of Byggforsk/Sintef and the absorption criteria were set to the new chairs accordingly. Stol uten person (sete oppslått) 1,00 0,90 0,80 0,70 0,60 0,50 0,40 0,30 0,20 0,10 0, f [Hz] eksisterende stol ny stol nedre grense ny stol øvre grense 2.5 Results Overall Reverberation Times (after/before renovation)

5 Absorption of Munch paintings before/after renovation: The measurements before renovation shoved absorption around 200 Hz. This absorption is not shown in the measurements after the renovation and remounting on a honeycomb backing. The measurements for frequencies over 2000 Hz showed almost no absorption, both before and after renovation. 3 Some Projects in Scandinavia 3.1 Stavanger (opening sept. 2012)

6 3.2 Kristiansand (opened january 2012) (Forprosjekt)

7 3.3 Aalborg

8 4 Summary, Halls in Scandinavia When comparing these three Scandinavian Halls of quite similar form and dimensions, we see that the main acoustical design topic of the decade(s) is THE BALCONIES, their form and most important: their shape. This also goes for auditoria like the new operas in Copenhagen and Oslo. References [1] T. Halmrast: Some Halls in Scandinavia Inst. Of Acoustics (IoA) 2006, Copenhagen [2] Norconsult: Room Acoustic Measurements in The Aula of the University of Oslo (in Norwegian) [3] Statsbygg, Oslo: Univ. Oslo, Domus Media Building Programme (in Norwegian)