When designing an acoustically sound space it is vital to account for any sound leaks that could be hidden. This is especially the case with doors and movable / folding walls. A great way to test for sound leaks is to “turn to the dark side.” Turn off the lights in a room adjacent to a bright room and look for light leaks through cracks and joints between panels, at the top seals, at the bottom seals and end seals. If you can see light coming through anywhere, there’s a good chance that the acoustics will suffer. In fact, they might suffer more than you’d think.
The following chart shows that even a very small leak can dramatically reduce the sound performance of a wall. The chart illustrates that a 1% leak would reduce the sound performance of a partition with the ability to provide 50 db Transmission Loss (approx. a 50 STC) down to only 20.
What is 1%? Here is an example: Imagine a manual operable partition in a paired panel configuration 24′ long by 8′ high. If the 2″ bottom drop seals had been left up, it would have about a 1% leak. This is a common set up issue with manual operable partitions and it results in significant reduction in acoustic performance.
The chart also shows that even a 0.1% leak will bring a 50 TL partition down to only 30. This is why a panel-only test (common with some operable wall manufacturers) should be carefully considered or even discounted.
Most operable wall panels have some type of vinyl seals at the top and bottom. These seals are the weakest part of the partition, acoustically speaking. If an operable manufacturer presents a panel test showing their STC (and not a acoustical lab test of the entire wall), the real life sound performance will be significantly lower then the test results show. A “dark side” test can be valuable and quickly reveal issues and prove that other tests are misleading. Next time you’re in a room with an operable partition, turn off the lights and look for leaks. Light leaks show sound leaks which can adversely affect acoustics. If you see a leak, other tests should be performed.
Automatically motor driven operable walls like Skyfold all but eliminate the potential for human error with setting up and therefore should have reliable and higher acoustical performance. Acoustical lab tests are performed on the entire wall assembly so real life performance will be much better. We, at Skyfold, pride ourselves in having quality products with extraordinarily high STC ratings to combat poor acoustics.