If someone were to ask me what I consider the most valuable life asset to be, I would have to say time. The second: flexibility. While as a society we seem to experience a significant time crunch, with our ambitions for a 24 hour, one hour, or even one minute period far outweighing the capacity of the poor hourglass, it looks like we are quite successful when it comes to flexibility. Which brings me to today’s topic: the flexibility of the office space.
Office flexibility can have many facets, intended on one hand to attract and retain young talent and on the other hand to allow companies to run their facilities more efficiently. Work flexibility can consist of working from home, in which case one’s office is only virtual, of hoteling, where one occupies an office desk on a first come first served basis, or of having the option to reconfigure space layouts as desired. When it comes to acoustics, this option of reconfiguring office space is of most interest to us.
Let’s say we have a bank of adjacent private offices, but depending on the hierarchy of those occupying them at a given moment, the facilities manager wants to have the option to move a wall left or right, in order to allow one office to become larger than the other. Or let’s say that, given the operations’ flexible needs, that same facilities manager may face the request of coming up with additional collaboration space. In that case, he or she may remove a wall separating two adjacent offices in order to provide a comfortable meeting room. These are not hypothetical scenarios, as acoustical consultants, we have seen them implemented again and again. When this kind of flexibility is demanded by clients, the design team more often than not makes use of demountable partitions. There is a crowd of manufacturers claiming that their demountable wall systems are more durable, easier to install, prettier and, last but not least, providing better sound isolation. Because, as you may have guessed, a wall that can be easily moved or removed is also quite light and unsealed, which will allow sound to travel effectively, despite a wall system’s considerable visual design features.
In order not to make this glorious exercise in flexibility an acoustical fiasco, here are a few things to keep in mind when working with demountable partitions:
1.) If a partition stops to the underside of the ACT ceiling, the sound isolation between the separated spaces will be only as good as the sound isolation through that ceiling, even if the wall panels may otherwise have better performance. To optimize performance, the tops of demountable walls should seal tightly to a gypsum wall board soffit, or at minimum, the tops of the walls should have a gasket system that compresses against the tiny gaps formed by the ACT grid, in order not to reduce the sound isolation further.
2.) If a partition has a door in it (generally this is the corridor partition), the sound isolation will be only as good as the performance of the door. In that case, evaluating the STC performance of the demising wall panels alone will not be of much value. The manufacturer should ideally provide field test data to show that the door closes tightly and the gaskets perform effectively, whether the door slides or swings. For reference, a typical framed swinging door with a well installed full perimeter gasket system, performs around NIC 30 (The NIC is a single-number rating that describes the sound isolation performance of an as-built construction; it differs from a Sound Transmission Class (STC) rating in that the latter is a laboratory measurement performed under ideal conditions. NIC ratings are generally about 5 to 8 points lower than STC)
3.) If a wall extends only to the underside of the ACT ceiling and/or it has a door in it, it is critical to use an electronic sound masking system, in order to achieve “confidential speech privacy” (where conversations may be occasionally heard but not understood.)
4.) If the use of a sound masking system is not suitable for a given space (e.g. in a conference room such system is not appropriate since it interferes with the need for speech intelligibility both in the room and via teleconferencing communication), some method of improving the sound isolation of the demising wall needs to be found. In general a stick built demising wall at conference rooms is expected to achieve a minimum STC 50 rating. Demountable partitions are rated between STCs in the upper 30s and STC 50. But remember, that if the wall stops to the underside of the ACT ceiling, the sound isolation will be only as good as that of the ACT. In that case, it is important to plan for a drywall plenum barrier that can stop the sound traveling through the ceiling plenum and, along with the ACT ceiling, it performs on par with the demountable wall.
5.) While sound masking may not be suitable inside a conference room, it is still desired outside of it, so that people cannot eavesdrop from the corridor. In this case, properly calibrated sound masking prevents those outside of closed spaces from hearing what is going on on the other side of the wall.
If these guidelines are followed and the demountable partitions are installed properly, it is very likely that confidential speech privacy will be achieved, whether in private offices or meeting rooms. On the other hand, if demountable wall systems are designed and installed poorly, acoustical privacy will suffer, resulting in low employee satisfaction, loss of productivity, and in some cases, unintended breaches of confidential information.