Acoustics in offices – get sound savvy

by Tania Wannenburg
Acoustics in offices get sound savvy

Acoustics products are an important part of office interior fit-outs, and it is important to properly understand the concept and apply appropriate sound treatments to create comfortable work environments.

Solutions to manage sound are necessary in any office environment where communication is important or where noise can distract people from their work. Acoustics play a big role in affecting productivity and behaviour, but selecting the appropriate solution and meeting different expectations are the tricky part.

“Each person has a different tolerance level to noise,” explains acoustic consultant Michel Batista from Subsonic Designs. “It is very difficult to design a space according to each individual’s requirements.

“Therefore acoustic design should be based on standards and guidelines for different spaces, and the importance of these should be emphasised to the client, as well as the consequences of such standards and guidelines not being implemented,” he states.

Communicate outcomes
Managing expectations are crucial to prevent a disconnect between what is expected from an acoustic installation and the real performance, according to Lauren Krüger, concept developer at Ecophon South Africa. “It is not like a chair that you can sit on and sign off. Sound is something that you can only really experience once you are in the space,” she says.

“An acoustic engineer can model up a space that can be very accurate, but the reality is that there is not always the budget on all of our projects in South Africa for that level of expertise,” she adds.

According to Aluglass Bautech’ Petunia Mpoza, insufficient knowledge of acoustic products may pose as a challenge that can lead to incorrect installations or solutions not fitting into the final design details.

Therefore, she recommends involving trusted manufacturers of acoustic products to give sound advice from the planning phase to the installation part.

Building materials, for example, influence the amount of acoustical absorption required to reduce or treat reverberation and noise, and an acoustical analysis of the space needs to be done before deciding on specific products. “Various tests apply for different solutions in determining the level or reverberation (reflected) sound within the space and providing an appropriate treatment that meets the necessary standards is essential” she points out.

Three guides for best practice:
SANS 10103:2004
–    The measurement and rating of environmental noise with respect to land use, health, annoyance and speech communication.
–    It gives both the design equivalent a continuous rating level for ambient noise in decibel and the maximum equivalent for different spaces in office buildings.

ISO 3382-3
–    Specifies a measurement method which results in single-number quantities indicating the general acoustical performance of open-plan offices.
–    Single number quantities determined are:
The rate of spatial decay of A-weighted sound pressure level of speech per distance doubling.    Target value: ≥ 7dB

Nominal A-weighted sound pressure level of normal speech at a distance of 4m from the sound source.    Target value: ≥ 48dB

Average A-weighted background noise level.    Recommendation: 35-40dB

Distance from speaker where the speech transmission index falls below 0,5.    Target value: ≤ 5m

The distance of comfort (e.g. between workstations).    Recommendation: ≤ 12m

Green Star SA Interiors Tool
–    Contains an acoustic credit component.
–    An acoustic engineer needs to measure acoustics and prove compliance.

Information courtesy of Ecophon

Planning sound treatment for offices
A space itself determines greatly what type of acoustic treatment is necessary. In a meeting room, speech needs to be clear, while in an open-plan area, one doesn’t want sound to travel.

Activity-based working, a trend that originated in the Netherlands, is currently very topical in South Africa, highlights Krüger. This trend sees office environments enabling employees to focus on different tasks in various zones suited for these activities. For example, there will be quiet areas for focused work, as well as meeting spaces for collaboration, with organisations allowing employees to move around to the appropriate spaces.

However, in such office environments, acoustics can greatly affect behaviour and productivity, according to Louis Lhoest from Veldhoen + Company, a Netherlands-based consulting firm on activity-based working. “Time and again, people fail to put enough effort into getting the acoustics right,” he states.

Understanding acoustics
Acoustics basically deals with two concepts – sound absorption and sound insulation.

    Sound absorption solutions lessen the level of sound within a room or an open-plan office.

    Sound insulation aims to isolate sound in a certain space to prevent noise from one space bleeding over into another, for example traffic noise into a building or sound between meeting rooms.

Application: Open office environments
In an open-plan workspace, it is necessary to add absorption and Krüger recommends treating two planes such as the ceiling and a wall. “The ceiling plane is ideal for adding absorption since it is not exposed to traffic, which limits wear and tear.

“Partitions also help to absorb sound if they have an appropriate thickness, but while desk-based screens give perceived privacy, they are not the most effective in terms of acoustics. In reality, a very high partition is needed to provide an effective acoustic shadow and block sound,” notes Krüger.
“The acoustic value of furniture lies in that it diffuses sound to various degrees. Sound doesn’t bounce directly back off it, but instead disperses,” she explains.

Application: Enclosed meeting rooms
“For achieving quiet and productive spaces within open-plan applications, where people can see each other while at the same time maintain privacy, an appropriate sound treatment would be an acoustic re-mountable partition system,” Mpoza suggests.

“A system that is quick and easy to install, remove and re-install with modular elements and flexible frame components would be ideal. It also has to achieve a sound pressure level between 35dB and 45dB,” she states.

When opting for glass walls, double-glazed shopfronts should be the standard, is Krüger’s advice. “One just needs to keep in mind that OFTEN walls are installed up to the underside of the ceiling, which means that sound can jump over it through the ceiling VOID.”

She warns though that sound behaves like water, so if there is even a little gap somewhere, sound will go through it. Therefore back-to-back plugs in adjacent meeting rooms are a bad idea, because they create a sound bridge between the two rooms where noise can leak through. In addition, a swing door always seals better than a sliding door.

Mpoza adds that gaps created by the installation of security cameras and fire sensors, as well as keyholes and windows, are weak points in terms of containing sound.

Inside, Mpoza recommends installing absorption panels with a noise reduction coefficient (NRC) between 0,5 and 0,85 to minimise sound reverberations and improve speech intelligibility. “These are cost-effective and aesthetically pleasing, and come in a wide range of colour schemes and designs,” she says.

Project focus: Aecom atrium
The atrium in the Aecom office building in Pretoria was originally only meant to be an entrance, but the company decided to use the floor space for a coffee shop and informal meeting space as well. However, this significantly heightened the noise levels in the atrium.

Architect Kobus Kunz from Hofman and Partners Architects came up with the idea of an “exploded” acoustic insulation feature that could double up as a type of artwork to also fill the space. The design consists of 220 square acoustic panels that are lined up horizontally and vertically, and makes for a visually stunning installation. Acoustically, the sound reverberation time has been dramatically reduced and speech clarity and intelligibility have improved.

Talking products
Some of the latest advances in the acoustics industry, according to Mpoza, are fully motorised and automatic acoustic partitions systems as well as customised products. “We are seeing increased partition heights of up to 12m for mobile acoustics partitions, which increases flexibility and ease of use, together with a wider variety of available finishes,” she says.

When selecting specific acoustic products, Batista highlights performance, quality and aesthetics as the key factors to consider.

“Use the product that would resolve the design issue best and only choose certified products and materials,” he advises. “Don’t just select a product because it says ‘acoustics’ – understand the purpose and the performance of such product. A product with an NRC 0.15, for example, will not provide the same results as one with an NRC 0.95.

“Rather seek advice from a professional than from suppliers whose first priority would be to sell their own products, whether or not they are the best for the application.”  

Five reasons for failure
In Batista’s experience, the top reasons why acoustic installations fail are:
1.    The design team changing the design against the recommendation of the acoustic consultant.
2.    The contractor using a product that does not meet the requirements as specified.
3.    Poor workmanship.
4.    A poor design by the acoustic specialist.
5.    A design not being followed correctly.

Full thanks and acknowledgement are given to Ecophon South Africa, Veldhoen + Company, Subsonic and Aluglass for the information given to write this article.

“Acoustics need to be applied as a layer over the design process,” says Lauren Krüger, concept developer at Ecophon South Africa.

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