That is not to say that open plan offices are perfect of course. And the biggest problem with them appears to be the lack of privacy they provide. The problem has been exacerbated recently by the trend to fit more and more people into offices, something that has become possible with the ubiquity of flat screens and laptops in place of space-hungry CRT monitors.

The lack of privacy in open plan offices can be an enormous problem. A recent survey by office equipment manufacturer Brother found that employees lose up to two hours a day because of distractions caused by colleagues, phones, email and the general white noise of office life. By contrast people working in total isolation, at home, were as much as 56% more productive. A more scientific study of 13,000 employees carried out in the US by John Olson of BOSTI Associates found that the single most important factor in determining productivity was the ability to do distraction-free solo work.

According to a report from the Commission for Architecture and the Built Environment (CABE) last year, people enjoy a 38% improvement in their ability to perform many tasks if they are in a workplace where acoustic conditions have been optimised. The same survey also reported that people perform 16% better in memory tests and 40% better in mental arithmetic tests, when they aren’t disrupted by undue noise. Other reports go even further. A study published in the British Journal of Psychology has highlighted the role that irrelevant noise plays not only in disrupting work, but also in increasing stress levels and decreasing job satisfaction.

What is interesting about the research in this area is that the things that cause the most stress, annoyance and distraction are those that are either irrelevant or over which people have no control. It’s not just about the level of noise, but the type. For example, the Scandinavian researchers Anders Kjellberg and Bertil Nordstrom found in a 1996 study that sudden noise was far more distracting than constant background noise. They also found that the noise of printers and shredders is only really annoying for the people not using the equipment. The same researchers also recount research that shows that colleagues’ speech is more of a problem when it is unintelligible or irrelevant.

Such distractions can prove very costly. According to the Brother survey, two thirds of workers complained they suffered up to 20 interruptions a day and just 1% of office workers ever managed to get through a day without being interrupted, compared with around 10% of home workers, the most isolated people you can get.

However, much as we are aware of the harmful effects of noise and much as many people claim they would like to work in enclosed offices (84% of them according to an Office Angels survey), the cost of space and the contemporary focus on teamworking dictate that the open plan is here to stay as the norm for most of them. Fortunately it is possible to reach some sort of balance between the often conflicting need for us to work in privacy but also communicate as part of teams.

Problems and solution arise first at an architectural level. Sound is prone to bounce off ceilings and follow sight lines so the way a building is designed can have a significant impact on noise levels in its interior. The type and shape of a building (and the culture of the organisation) is often beyond the control of the organisations that inhabit them so, regardless of its architecture, there are five basic steps that a facilities manager or interior designer can take to deal with problems of noise in a building.

1. Ceiling systems

High performance ceiling products with significant articulation class (AC) ratings and noise reduction coefficients (NRCs) are readily available. AC ratings determine how well a ceiling reflects sound. NRCs determine how well a surface absorbs sound. It is also important to avoid HVAC and lighting elements that can act as reflectors of sound.

2. Sound masking systems

Sound masking systems generate a level of white noise that helps to minimise the disruption caused by speech and sudden or ‘impact’ noises.

3. Systems furniture

All furniture will absorb some level of sound, but screens and partitioning is by definition particularly effective. Properly specified, such interior architecture can absorb around 85% of ambient, intrusive sound, which is particularly important where teams who may need to communicate on an ad hoc continuous basis are situated near to people from other disciplines or who need to work quietly. Remember that low, desk-up screens have their part to play but serve mainly to break up space and add colour to an office.

4. Flooring

Hard flooring is often a problem in offices. As a general rule, carpet is far better at absorbing noise than hard flooring. Carpet most obviously dulls impact sound or ‘footstep noise’ by reducing the sound reflection that is characteristic of hard surfaces. A contract carpet with a cushion backing can absorb as much as 36dB of impact sound. Whereas, (according to research carried out in the US) carpet backed to a hard substrate has a noise reduction coefficient of around 0.25 (where a coefficient of 1 represents 100% sound absorption) or in Milliken’s own terminology a reduction in the region of 20 -25dB.

Hard flooring will typically achieve a reduction in just single figures. Anybody who would like to investigate further is referred to BS EN ISO 140-8:1998, the appropriate standard. Additionally carpet absorbs ambient sound and can be up to 70% effective, for high pile carpet with thick underlay, according to research carried out in the US.

Interior design

It’s not only what you’ve got, it’s how you use it. Space planning can play an essential role in creating a balanced acoustic environment. A well designed layout will minimise sight lines and also group people sensibly. It will take account of trends such as the use of flat screens and laptops which tend to create higher occupation densities and accommodate for them. Specifying quiet work rooms and break out spaces can be essential (if properly monitored and managed) so that people can work in the right environment for the job in hand. A good designer will also use screens and partitions intelligently to provide the right balance of privacy and interaction.

Glossary

Here are a few of the most common terms.

Articulation Class (AC) – Rating system used to evaluate open office acoustical ceilings based on speech privacy. Values range from 100 to 250, the higher the better.

Articulation Index (AI) – Measurement of speech privacy between open plan workstations. Values range from one to zero, with lower meaning better performance.

Noise Reduction Coefficient (NRC) – Rating system to determine sound absorbency of a material over the speech frequency range at 250, 500, 1,000 and 2,000 Hz. The higher the number, the more absorbent the product.

Sound Transmission Class (STC) – Rating for construction elements (doors, walls, windows, etc) based on their ability to reduce sound. The higher the number, the more sound is blocked.

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