GIK Acoustics is an acoustic treatments company, yet we often get questions about soundproofing, a very different subject. We put together this video as a general guide to help point people in the right direction.
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"People often confuse soundproofing and acoustic treatment and it’s easy to understand why. Both require an understanding of the science of sound and many products that are meant to be used for acoustic treatment are held up as soundproofing solutions.
The truth is, soundproofing a room to stop sound, and acoustically treating a room to make it sound better, are completely different processes that require different tools and methods.
Acoustic treatment is about improving the sound quality within a room for a clear and pleasant recording or playback. We accomplish this by eliminating reflections that interfere with the original audio source.
In contrast, Soundproofing is about stopping soundwaves from traveling between rooms or between the room and the world outside.
GIK products are all designed to be used for Acoustic Treatment and while they’re great for controlling sound within a room they’re not meant to isolate rooms for soundproofing.
Thick acoustic treatment is good for absorbing bass reflections inside the room (and will help to dampen the noise bleeding into the room), but you’ll need more than that for the sub bass frequencies vibrating through your walls. If sound from another room is bothering you, it’s probably at lower frequencies, in the bass range or lower midrange as High treble frequencies are much easier to stop than bass frequencies.
Even normal drywall construction will probably perform very well in the top octave of music, of ten to twenty KiloHertz. But each subsequent lower octave will have roughly half the isolation of the octave above it.
In other words, 5-10kHz will have about half the isolation of 10-20kHz. 2.5-5kHz will have about half the isolation of 5-10khz, and so on. So by the time we get to the bottom octaves our work will be cut out for us.
There are three proven methods for effective soundproofing at bass frequencies: Mass, Airtightness, and in some cases Decoupling. Note that all these techniques involve construction methods that change how the room is built. These methods will be very specific and probably counterintuitive to builders used to conventional techniques.
Mass is a very low tech but proven way to block sound. Drywall is the most cost-effective way to achieve mass, and multiple layers of drywall is usually the best way to stack a lot of mass very easily.
We can also use Constrained Damping Layer materials, like Green Glue, between the layers of drywall for even better performance.
Airtightness is important because if air can get through, then so can sound. Here acoustic caulking is useful. Other strategies like weatherstripping around a door can also help, and attention to HVAC systems is important. If you try to isolate a room and it shares an air duct with another room, that will be a big problem. And we can’t completely seal the room -- oxygen runs out quickly in a small, airtight room with a singer breathing deeply and heavily during each take.
Decoupling the room prevents flanking noise, which is where low frequency energy passes through the structure of the room itself, like the drywall mass, framing, and ceiling/floor assemblies. There are various strategies to improve decoupling, including a double wall, room-inside-a-room build, or also using things like resilient channels between the drywall and the framing to improve decoupling.
Build technique can also help you get more soundproofing out of your materials. This diagram shows you the performance of a few different build strategies. Note the different STC ratings for each build. STC simply means “Sound Transmission Class” and describes how many decibels are isolated. It’s a much more useful parameter than the more common NRC ratings for audio purposes. So STC40 means that construction gives 40dB less sound outside the room than in.
Normal construction for an interior wall is STC 33, with framing and a layer of drywall on each side. The STC40 diagram shows double-wall construction, where each wall is the same. There is clearly 10dB improvement. "
However, with the exact same materials installed in a different configuration, we can instead achieve a 30dB improvement. This 20dB gain means the sound will be 100 times softer!
This is just one example of the counterintuitive details to maximize soundproofing. To isolate the bass frequencies required for music, you need a good design and careful, precise construction. The experts at GIK specialize in room acoustics so there’s little more they can tell you about soundproofing beyond what we’ve already covered in this video."