Open Plan Office Acoustic Design
The aim of our articles are to break down acoustic design concepts and terminology as simply as possible, without going too far into the mathematics and every nitty gritty technicality, that acoustic consultants usually love to get stuck into.
So please, if you’re an architect, contractor, developer, planner… or really anyone who occasionally needs to dabble in acoustic design and assessments… then read on…
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Acoustic Design for Speech Privacy in Open Plan Offices
How can a fair level of speech privacy still be achieved between colleagues when there are no walls? How can we prevent a build up noise from giving everyone a headache?
Reducing the Spread of Sound from Speech
Reducing the reverberation time is critical, linking to the level of sound energy ‘bouncing’ around the room. By adding sound absorbing finishes and furniture, we can minimize speech sound travelling over distance by suppressing sound reflections from the room. Reducing reverberation can soften the sound too, creating a less harsh / bright sounding environments which can be preferred for concentration, and increasing speech intelligibility in our immediate vicinity (but increasing speech privacy from others sitting further away.
Suppressing 1st order Reflections
Linked to the reverberation time, suppressing reflections is achieved by using sound absorbing material. The critical difference is the location of the material. Whilst it is good for reverberation to spread treatment around the room, some cleverly placed treatment can be used to enhance the noise screening effect of desk dividers and furniture by minimizing sound reflections of surfaces over and around them.
Screens and Containing Sound
Screens which block the line of sight between a ‘source’ and a ‘receptor’ aid in minimizing ‘direct’ sound. Screens are best placed close to the source or receptor and can be used around group working areas to contain sound effectively. Even partial height desk dividers are effective by reducing sound reflections off the desk and diffusing sound such that it can reach the acoustic absorption around the room more efficiently.
Many of the points above can be tackled without an abundance of specialist products, through careful design of the layout. For example, the building structure can act as a noise screen if separate groups are placed around the corner from one another. Shelving and lockers can be used as screens or placed to prevent large groups congregating in area near quiet workers. Similarly, noise-sensitive workers can be placed in areas further away from more talkative groups (particularly those who are regularly on the phone), or those using noise equipment.
Masking Speech with Background Noise
External noise sources (such as road traffic) can provide some useful background noise, dependent on the context. An office close to a motorway should experience a relatively constant noise level without tonal or intermittent qualities. On the other hand, a city center road with intermittent traffic, or regular ambulances, buses, and car horns, may be more of a distraction.
Building Services Noise
In a mechanically ventilated building, a consistent unremarkable broadband noise can be achieved through the air handling system. On the other hand, an AHU with a tonal noise quality may have an adverse effect, as would intermittent noise from pipework, toilets, hand driers…
Sound Masking System
Artificially injecting white or pink noise into an open plan office by a series of ceiling mounted loudspeakers. The use of a broadband noise is not dissimilar to the noise of an air conditioning system, providing a steady unobtrusive noise source which is barely noticeable, but helps to mask the intermittent and intelligible speech of a neighboring colleague.
I hope you enjoyed this short article, and keep an eye out for more articles on the common questions that I get asked by clients in my job as an acoustic consultant. Feel free to connect and message me through LinkedIn, send me an email at email@example.com, or through our Contact Us page.