Office design: Good acoustics require an effort

Large offices offer many advantages, but good acoustics isn’t one of them. Consequently, it is difficult for employees to concentrate, and it impacts their well-being, but with the right measures, the acoustics can be significantly improved.

If you work in an open-plan office, you might well be familiar with the problem already. The sound of high heels on a hard floor, colleagues talking, or noisy telephone conversations. All sounds which can make it difficult to concentrate on your work. And the large number of sound sources in the expansive offices is not the only challenge, says Niels Kappel, a product developer working in Troldtekt A/S’s technical department:

“Acoustically, large open-plan offices are a mess, and it’s not always easy to design one’s way out of it. This is because the larger the room, the longer the reverberation time – i.e. the time it takes for a sound to die out in a room. In other words, the larger the office, the longer the reverberation time – and long reverberation times are synonymous with poor acoustics,” he says by way of explanation.

Sounds that take a long time to die out mix and interfere with new sounds. The classic example is a largish gathering, where you have to speak increasingly loudly to make yourself heard and understood. This can have a detrimental effect on employee productivity as well as on job satisfaction at the office.

The good news is that a lot can be done to improve the acoustics in large offices. The bad news is that there is no quick fix.

“It requires significant measures to tackle the problem of bad acoustics once the office is there. Sometimes people end up erecting partitions in order to mitigate the effects of poor acoustics. However, in practice, the sound simply travels above them,” says Niels Kappel.

It’s all about absorption

According to Niels Kappel, the most effective solutions for improving the acoustics in open-plan offices comprise several elements. In many cases, it is a question of having a sufficiently large absorption area – i.e. cladding on walls, floors or ceilings that does not reflect the sound waves, but which absorbs them. The sound absorption coefficient of different materials matters.

“One example is ceilings made of perforated plasterboard. Here, the holes act as the absorption area, but they cover only 30 per cent of the surface, while the rest is hard and reflects the sound waves straight back. That’s why perforated panels are rarely enough to ensure good acoustics,” he says.

In general, the reverberation time depends on the structures of the surfaces in the room. Hard, smooth surfaces like concrete and plaster result in long reverberation times, while materials with an open surface structure – such as Troldtekt acoustic panels – result in short reverberation times and thus excellent acoustics. In practice, a concrete wall absorbs only 1-2 per cent of the sound, while a construction with Troldtekt with a mineral wool backing will usually absorb 80-90 per cent of the sound.

There are various recommendations regarding the size of the absorption area in office landscapes:

• According to the Danish Building Research Institute (SBi), the area should correspond to 1.1 times the floor area – in other words the absorption area should be 10 per cent larger than the floor area.
• The Danish Working Environment Authority’s recommendations differ slightly. The authority recommends that the absorption area is 0.8 times the size of the floor area, if the total office area is less than 300 square metres. In larger offices, the absorption area should be 0.9 times the floor area.

Decor and work culture are also tools

In addition to ensuring enough sound-absorbing material on the walls and ceilings, Niels Kappel says you can also do a lot by working with both the decor and the work culture.

“Carpeting the walkways can be a very good idea, because it limits the noise from employees moving around the office,” he says.

Niels Kappel also mentions shelving with books as being extremely effective at absorbing sound, but is well aware that books tend to not feature prominently these days in either his own or other workplaces in the digital age.

“In our office, the volume of telephone ringing tones is turned down, so they don’t disturb unnecessarily. In addition, you can come a long way with unwritten rules such as avoiding standing meetings in open-plan offices, and instead designing environments with several flexible spaces which can be used, for example, for informal meetings,” he says.

Calculator: Understand the acoustics in your office

If you want to calculate the acoustic consequences of dimensioning and using different materials in your office environment, try using Troldtekt’s acoustics calculator.

To use the acoustics calculator, you need to know the dimensions of the room as well as the materials that have been used – or which you plan to use. In the acoustics calculator, you enter the various data for the room, and the acoustics calculator generates an easy-to-understand report with a list of reverberation times, absorption area and other useful information about acoustics. The report can be emailed to you or you can print it directly.