There has been a welcome move in recent times towards ensuring that the wellbeing and comfort of future occupiers is considered carefully in the design of both new and refurbished offices. Items which are most commonly discussed are lighting, ventilation and cooling, flexibility in spaces and furniture, the use of technology, and even bio-philia.
What often appears to be overlooked or underrepresented in these discussions is the issue of acoustics.
Over the last couple of decades, the office environment has moved from highly cellular spaces, where everyone has their own personal space and is separated from the people around them, to a much more open plan and increasingly flexible environment. In many cases people no longer have permanent workstations, and meeting areas are increasingly part of the open plan environment.
In many discussions noise is cited as one of the key considerations for the happiness and comfort of occupants, which is strongly linked to both productivity and bio-physical wellness (links have been drawn between excessive noise and issues with the nervous system, endocrine system, and cardiovascular disease). The FIS Guide to Office Acoustics claims that 10 times more people complain about noise in open plan offices (60%) when compared to cellular offices (6%), and BREEAM, Ska, LEED and the WELL Building Standard all incorporate credits for good acoustic design under health and wellbeing.
The acoustic issues associated with open plan offices are exacerbated by the trend for industrial feeling finishes, and the desire for hard finishes such as exposed concrete soffits – sometimes for aesthetic purposes, and other times for energy purposes to provide thermal mass. This can result in reverberant noise build up (excessive ‘echo’) and issues with speech intelligibility.
In order to provide a comfortable environment for occupants acoustically, a number of factors need to be considered.
How are the spaces going to be used?
It is important to understand what kinds of activities are proposed for the various spaces. Is the office primarily a quiet space for concentrated work, or is everyone on the phone or in lively discussion for the majority of the day? Where is there a need for speech privacy, and where is it more important to have a lively ‘buzzy’ atmosphere? Will it be a combination of the two with potentially conflicting goals?
In terms of cellular spaces, are they intended for small one-on-one meetings, larger internal meetings, client facing presentations, or video-conferencing? All of these uses would require different levels of acoustic separation, different amounts of acoustic absorption, and different background sound levels.
A good client briefing and direct discussions between the client representative and the acoustic consultant at the early stages of a project can make all the difference in getting the right result for occupants on completion. Audio demonstrations are particularly useful in this process as they allow the client to actually hear what different construction types or treatments will sound like in the finished building.
What about flexibility?
We established above that different uses have different acoustic requirements, but what about when flexibility is required and a single space is to be used for a number of different scenarios? In many cases, the best option in offices is to design to the most stringent use. However, again, a good client briefing may mean that compromises can be made on some (typically more infrequent) uses, resulting in a saving to the project comparing to designing for the ‘worst case scenario’.
Another key area where flexibility and acoustics often come into conflict is that of movable partitions. Typically, these tend to be used to separate meeting rooms, with a view to having the potential to open up the rooms into one large space. However, the level of acoustic separation that is achievable with movable partitions is inherently limited by a number of factors, such as the lightweight nature of the panels, the seals and joints, and the interfaces with the surrounding elements.
As such, where movable partitions are proposed, it is important to understand the limitations of the design, and manage the use of the spaces accordingly.
How do we approach speech privacy?
The most common (and arguably the most important) acoustic issue in offices is that of speech privacy. Whether the end user needs to have a phone conversation in an open plan office without being heard at the other end of the space, or they are having a confidential discussion in meeting room or ‘quiet pod’, occupants need to have confidence in their acoustic environment.
The two key variables in speech privacy are sound reduction and background sound levels. In an open plan office, acoustically absorptive treatment and partial height screens can be used to limit the amount of sound travelling around a floorplate. In cellular spaces, well constructed and detailed partitions and doors can provide a high level of acoustic separation. In both instances, if the background sound levels are too low (ie, the space is very quiet), it will be very difficult to provide a good level of speech privacy.
However if background sound levels are too high, this in itself can be disturbing, and so providing an appropriate level of speech privacy for the use needs to be a balance of both.
Historically, building services systems have been relied upon to provide a reasonable level of background noise in offices, particularly where fan coil systems are used. Background sound levels being too low typically only became an issue where low noise systems such as passive chilled beams were being used. However, in the current climate where sustainability and energy usage are critical, even buildings with fan coil systems can have issues with low noise levels as systems typically ramp down with occupancy, and in some cases switch off in the early evening.
As such, the introduction of sound masking systems (sometimes referred to as ‘pink noise’ or ‘white noise’ systems) is becoming more prevalent. These systems include an array of speakers introducing a low level of background sound into the relevant space – the spectrum can be targeted to ensure it provides optimum masking while being bland and unobtrusive. As it is independent of the building services systems, sound masking can provide a reliable consistent background level in all key areas over the relevant time periods.
A combination of ensuring good control of sound transmission and a consistent background sound level is what leads to good levels of speech privacy in office environments.
And Room Acoustics?
The other main issue that occurs in both meeting rooms and open plan areas is that of room acoustics – which includes the need for acoustic absorption to control reverberation and reflections.
Typically, spaces with little or no acoustic absorption are too lively and result in problems with speech intelligibility and excessive sound transmission. In addition to this, the increase in the use of technologies such as tele- and video-conferencing means that acoustic conditions within meeting areas is more critical. In some cases, these spaces may seem acceptable in person, but on the other end of a video conference connection, excessive reverberation can cause significantly more problems.
Similarly in entrance areas – typically these spaces have hard finishes such as stone flooring, glass facades and partitions, and plasterboard ceilings. While in the majority of cases, we don’t want these areas to be too ‘dead’ to maintain a lively atmosphere, if the reverberation time is too long noise build up can make the area uncomfortable, and cause speech intelligibility issues at the reception area.
The inclusion of some acoustically absorptive treatment is therefore beneficial, and becomes more critical if the entrance area is multi-functional – the inclusion of café areas, breakout meeting areas, or other uses which make the space more noisy or more noise sensitive.
It is therefore important to carry out modelling and predictions of how sound will behave in key areas to determine what acoustic finishes will be required, and where they will provide optimal benefit.
In summary, in order to ensure that a new or refurbished office space provides a good level of acoustic comfort, the following things need to be considered:
- Ensure a good acoustic consultant is an integral part of the design team from a relatively early stage
- Allow and encourage direct discussions between the client team and the acoustic consultant, including audio demonstrations where appropriate
- Provide appropriate levels of sound insulation between spaces by adopting appropriate constructions and details for the relevant areas
- Ensure background noise levels are neither too high nor too low, either by selecting the building services systems to suit, or by installing a sound masking system
- Include appropriate acoustic finishes in key areas – areas requiring acoustically absorptive finishes are typically entrance and reception areas, open plan offices, and meeting rooms.
Going through this process, and incorporating the appropriate constructions and treatments is likely to result in a good acoustic environment, meaning better comfort for the occupants, thereby increasing wellbeing and happiness.