Gothenburg Opera House

SINGLE® Absorbents dressed in fabric

If you wish to add colour to an entire wall or if you wish to smarten up your working environment at the same time as improving the acoustic quality, you go for SINGLE®.

Acoustics in a can? Yes, it actually works, and with well-balanced insulation and a hefty dose of electronics it’s possible to transform both the volume and the overall experience into something completely different to what the builders left behind.

When Göteborg Opera was inaugurated in 1994, having the best possible acoustics had been a guiding principle of the building. In the auditorium, that is. That their ambitions were not quite so high when it came to the rehearsal spaces, or that costs had had to be cut, became clear from a very early stage. Both the orchestra and choir’s halls were small with regard to the number of musicians and chorists. They tried to solve this problem by all manner of measures, but had no success in creating a tolerable working environment. It even got so bad that the choir hall was reported to the Swedish Work Environment Authority in 2011. The high noise levels meant that members of the choir risked damaging their hearing.

Hearing protectors added insult to injury

The same year, violist Magnus Pehrsson celebrated his first ten years in the orchestra, of which he had suffered from tinnitus for eight – a result of the excessive levels of noise. Magnus summarises his first year in the orchestra’s rehearsal hall: “Too many people with too many instruments playing far too loud in a room that was too small. Not only was the volume too loud; people also had problems hearing one another between the sections, which meant that it was hard to find a natural dynamic in the orchestra. Internally, it also led to friction; those who played instruments that are tonally softer – such as the strings – were constantly getting annoyed at the brass and percussion sections for playing too loud. ” Later, once they gave up on them finding the right acoustic measures, more and more of musicians started bringing hearing protectors to rehearsals. And if you play with hearing protection, then you lose control over your own dynamics – what Magnus calls “skipping the subtleties” – which serves to drive the volume up even more. “Unfortunately we fell into a downwards spiral. Yet I still felt like I had a long life ahead of me as an orchestral musician. And I wanted to stay at Göteborg Opera.”

But a solution was in sight. In 2013 a new electro-acoustic system from Yamaha was tested at the Royal Swedish Opera in Stockholm, where they had had similar problems, and after paying the latter a study visit the Gothenburgers decided to install the system at Göteborg Opera too. The concept is simple. First, it is ensured that the actual room has a controllable base acoustic – dry without being mute. Then a microphone system is installed, which captures the sound in the room and sends it to two processors: one takes care of the first reflections and the second adds a faint echo. Then the sound is sent back to the room where it is played out through a large number of speakers to give a sense of natural reverb. Ingemar Ohlsson at Audio Datalog made the first acoustics calculations and, with the help of a mix of diffusors and absorbents, insulation in the ceiling and cladding to the beams, they managed to reach a 0.5 second reverb in the room. After that, Stockholm company Audile installed the electronic rigging. Four omnidirectional condenser microphones were suspended in a small square over the orchestra, with four cardioid microphones in a larger square out towards the corners of the room.

A mix of different acoustic products

There were 16 wall-mounted speakers, symmetrically positioned approximately three meters up and facing inwards, supplemented by 20 further speakers on the ceiling facing downwards – all to cover the room as evenly as possible. The 36 smaller speakers also had some help in the lower registers by four subwoofers, hung from the ceiling in a large square. In order for the sound to feel as transparent as possible, it was also split up into 40 channels; one per speaker. Using a control panel it is then possible to select the reverb based on the number of musicians in the room: whether it’s an orchestra, orchestra plus choir or a small ensemble, in which case the reverb goes from 1.1 up to 1.5 seconds.

You leave work more refreshed

Since installation in August 2014 different degrees of insulation and reverb have been experimented with, and Magnus Pehrsson says that the sound environment in the rehearsal room was really noticeable when the orchestra would then come out to play in the auditorium. “When it was at its most insulated it could get a bit screechy when the orchestra sat in the pit, and the conductor had to do a lot of work to tighten up the dynamics.” Of course, the best thing would have been to have the same acoustics in the rehearsal room as those out in the auditorium, but the laws of physics are pretty uncompromising in that respect. The room is too small for a full orchestra – no electronics in the world can change that – but the fact that they were nevertheless able to improve the musicians’ experience is clear when Magnus points out one detail not directly linked to hearing, but which still shows the effect of the added reverb.

“That little extra reverb means that it feels more like in the auditorium; that you can loosen up a little, play a little bit more relaxed. A number of musicians still use hearing protection, both during rehearsals and in operas with a full orchestra, but the number of those who do so is considerably less than previously. I ask Magnus Pehrsson to rate the difference before and after based on the ten-grade pain scale used in hospitals.  “It could probably have been a 7 or 8 during certain powerful passages, but we’re probably down to a 4 or 5 now. I wouldn’t say that the problem is entirely solved, but in making the orchestra’s daily work that bit easier it has made a huge difference, and seeing as we sit there every day, every improvement means a lot. Now I go home with more energy and less of a headache.”

Project facts

Acoustics consultant: Ingemar Ohlsson, Audio Datalab
Absorbents: A.M. Acoustics Single
Diffusers: Svanå miljöteknik
Processors: Yamaha AFC3
Amps: Yamaha XMV8280 och XP7000
Microphones: ADK Zigma3 x 8
Speakers: JBL 8” x 36 och Yamaha 18” x 4