Achieving effective acoustics in the workplace
Research indicates that poor acoustics negatively affect employees’ productivity, stress levels and morale. For example, a study conducted by Finland’s Institute of Occupational Health shows that unwilling listeners demonstrate a five to 10 per cent decline in performance when undertaking tasks requiring concentration. Niklas Moeller, vice-president of K.R. Moeller Associates Ltd., explains more.
Of course, good office etiquette (e.g. using a reasonable voice level) helps to control noise. However, people always create sounds as they perform tasks. The remainder of the acoustical burden has to be borne by the workplace design using a three-pronged approach called the ‘ABC Rule,’ which stands for absorb, block and cover.
Today, the term ‘collaboration’ is often invoked to justify the elimination of many elements of this time-honoured rule, but reports such as Gensler’s What We’ve Learned About Focus in the Workplace (2012) show that most employees still spend more than half their time on individual work that requires concentration. When engaged in these activities, they need to be free from distracting noises. Rather than benefiting from overhearing each other, the Center for the Built Environment (CBE) found that the majority consider it irritating and disruptive. Employees are also concerned by their lack of speech privacy.
Given the apparent discrepancy between current design trends and occupant needs, a review of the ABC Rule seems timely.
‘A’ stands for adding ‘absorption,’ which reduces the energy and, therefore, the volume of noises reflected off various surfaces back into the space, the length of time they last and how far they travel.
To meet this requirement, it is important to invest in a good acoustic ceiling tile and ensure consistent coverage throughout the facility. Also, limit the lighting system’s impact on the ceiling’s performance by selecting an indirect system that incorporates a minimum number of fixtures while still meeting the lighting requirements. Minimise the use of hard materials, such as glass and metal, because these reflect noise and conversation, causing them to be heard over greater distances. Use absorptive partitions, at least inside and above the work surface, and install soft flooring in high-traffic areas.
‘B’ is for ‘blocking.’ Closed rooms use walls and doors for this purpose, but blocking is also a relevant technique for open plans.
Workstation partitions are often the biggest casualty of today’s design trends. However, they are an essential noise control strategy where people are working in close proximity to each other. No other acoustic treatment has a similar effect over very short distances; therefore, if one dispenses with barriers, one reduces the acoustic performance of their space in a way that cannot be offset by other design decisions.
Partitions that are 60 to 65 inches (1.5 to 1.65 metres) are effective because they extend beyond seated head height, though using taller partitions in high traffic areas can be beneficial. One should also try to minimise direct paths of sound transmission from one person to another by seating employees facing away from each other on either side of partitions.
Layout can also be used to isolate noise; for example, to separate collaborative areas from those used for focus work.
Most people are already familiar with the strategies described above. Fewer understand the role sound itself plays in achieving effective acoustics.
Indeed, many believe the goal is to make their facility as silent as possible. However, due to improvements in construction materials, as well as quieter office and mechanical equipment, the ambient – or background sound – level in the majority of offices is already too low, leaving employees trying to work in library-like conditions in which even speech and noise at low volumes can easily be heard across distances of 9 to 15 metres (30 to 50 feet) or more.
The ‘C’ in the ‘ABC Rule’ stands for ‘covering up’ unwanted noises by establishing an appropriate background sound level, which is typically between 42 and 48 dBA in commercial interiors. This requirement is met by installing a sound masking system.
Sound masking technology consists of a series of loudspeakers installed in a grid-like pattern above the ceiling, which distribute a sound most often compared to that of softly blowing air. Though the sound is audible, occupants perceive treated spaces as quieter because raising the background sound level reduces the intelligibility of conversations and the disruptiveness of noises, either by covering them up completely or by reducing the magnitude of change between baseline and peak volumes in the space. The sound’s efficacy is increased by virtue of being specifically engineered to mask the frequencies in human speech. It also creates a more consistent acoustic environment by minimising variations in sound quality across the facility.
A Powerful Combination
Each of these methods contributes differently to overall acoustic performance. Therefore, they are most powerful when used in combination and the root of any problem usually lies in the omission of one or more of these methods or their imbalanced application.
If an organisation moves into their facility and finds that the initial design or construction has failed acoustically, implementing ‘Cover’ might not be the only improvement necessary, but the only feasible choice. Budget pricing for sound masking is low relative to retrofitting other treatments and post-occupancy installation can be handled with only minor disruption. In addition, this technology can not only be used to improve open plan acoustics, but also to increase privacy for private offices and meeting rooms. Unlike closing the ceiling or extending walls to the deck, adding masking will have no impact on other building systems.
That said, it is always preferable to plan for acoustics during the design phase and take full advantage of the ways in which the various acoustic treatments can complement each other. For example, high spec walls and plenum barriers can be replaced by a combination of floor-to-ceiling walls and sound masking, achieving the same or better privacy while reducing the cost of initial construction and future changes.
In short, implementing the ABCs from the outset allows one to derive the maximum benefit for the minimum investment and help to protect an organisation’s greatest asset: employees.
Niklas Moeller is the vice-president of K.R. Moeller Associates Ltd., manufacturer of the LogiSon Acoustic Network sound masking system (www.logison.co.uk). He also writes an acoustics blog at www.soundmaskingblog.com
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