Achieving Acoustic Comfort in Green Buildings
Effective acoustics are essential to workplace satisfaction and performance. As such, they should be a top design priority, particularly in green buildings where the mandate is not only to use fewer resources, but to create environments that are healthy and nurturing for occupants.
However, surveys conducted by the Center for the Built Environment (CBE), University of California Berkeley, show that green building occupants are generally more dissatisfied with acoustics than those in traditional structures.
The reason for this deficiency seems to lie in the fact that many green design practices unintentionally contravene the methods acoustic professionals typically use to control noise and improve speech privacy: absorb, block and cover.
Absorptive materials reduce the volume of noises reflected back into a space, the length of time they last and the distance they travel.
Because the ceiling is usually the largest uninterrupted surface in a facility, using a good absorptive tile is key. However, many green buildings have open ceilings. Research whether this decision will have the desired heating/cooling benefits and, if an exposed structure is still desired, treat an appropriate percentage of the deck with an absorptive material. Generally speaking, this strategy has an impact, as do vertical baffles.
Workstation panels should also be absorptive, particularly if there is no acoustical tile. If the space is narrow in order to promote natural light penetration, use absorptive panels on select walls in order to prevent noise from ricocheting between the exterior wall and the core. Use soft flooring to reduce footfall noise, at least in high traffic areas.
Blocking noise is typically achieved using walls, doors and other physical structures. However, green buildings feature more open plan that their traditional counterparts.
In open plan spaces, workstation partitions above seated head height (60-65 inches) are essential to attenuate the noises passing to an occupant’s nearest neighbors. If they are shorter, they do little more than hold up the desks.
Where daylighting is a concern, use absorptive panels up to a 48-inch height and top them with 12 inches of glass. The top introduces a reflective surface, but the reduction in absorption relative to the increase in blocking is an acceptable compromise. Also, ensure the panels have a high Sound Transmission Class (STC) rating and are well-sealed along any joints, with no significant openings between or below them.
If there is no ceiling, build walls to the deck. If there is a suspended ceiling, walls can stop at the ceiling, providing a covering strategy is implemented (see below). Walls should have a high STC rating to prevent airborne noise transmission; doors and interior windows should meet the same standard. Ensure that any gaps are carefully managed (e.g. do not locate penetrations such as outlets back-to-back on opposite sides of a wall) because these can significantly compromise the wall’s performance.
While many people believe they can achieve effective acoustics by only absorbing and blocking, these strategies simply reduce and contain noise. One must also ensure that the background sound level in the space is sufficient to provide speech privacy and reduce the amount of disruption caused by the remaining noises in the space.
The background sound level in most conventional offices is already too low. The use of high-efficiency heating and cooling systems means that it is generally even lower in green buildings.
Install a sound masking system to address this deficiency. This solution uses a series of loudspeakers to distribute a continuous sound that has been specifically engineered to increase speech privacy. It also completely covers up noises or reduces their impact by decreasing the amount of change between the baseline and any volume peaks in the space. Most systems also provide paging and music distribution.
Using a sound masking system can help support other sustainable efforts, especially when included in the design stage. For instance, masking increases noise isolation in open plans. Natural ventilation can be employed. It also paves the way for using demountable walls, contributing to the space’s flexibility and reducing waste following renovations.
About the author: Niklas Moeller is the vice-president of K.R. Moeller Associates Ltd., manufacturer of the LogiSon Acoustic Network sound masking system. He also writes an acoustics blog at www.soundmaskingblog.com.
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