Keeping the peace: acoustic insulating20-01-2023
There’s nothing worse than being subjected to the muffled boom-boom of someone else’s music, or the neighbour’s dog barking all day… Or not being able to turn your own music up without someone banging on the door…
It’s something we’re asked about frequently, so in this post we want to outline the various factors you need to take into account in order to insulate your room effectively. IMPORTANT: this article is to keep unwanted sound OUT of the room and to keep the sound you produce IN the room.
If you want to insulate your room properly, it boils down to a couple of basic principles:
Make it airtight and heavy
Firstly, your room has to be airtight. Ultimately, sound is simply the movement of air, so if there is a way for air to escape the room, sound will too. However, just because your room is airtight doesn’t mean it’s soundproof. When sound bounces against a surface it causes vibrations. If these vibrations are strong enough to excite the air on the other side, audible sound will be transmitted through the surface. The main way to combat this problem is to make the surface heavier (add mass). The heavier the surface, the more difficult it is to excite, hence less sound is produced on the other side of the wall. As a rule of thumb, doubling the surface mass results in a 6dB reduction in transmitted sound.
Decoupling a room or wall
Luckily there is another way to insulate a room without having to add outrageous amounts of insulating materials – and this is by decoupling or separating the surfaces from each other so that they don’t touch. The air gap prevents vibrations passing between the surfaces. However, floors can’t just hover above an existing floor, so to minimize sound transfer through connection points, anti-vibration connectors are used. These can be of cork, rubber or other absorbent materials which will act as a spring between the two layers to minimize vibrations – and thus sound transfer. If you’re looking for significant sound reduction, decoupled surfaces are the way to go as you can achieve much greater sound insulation using noticeably less surface mass.
Doors & windows
Doors and windows are basically holes in the construction where sound can easily pass through, and so typically the weak spots in your sound insulation scenario. Acoustic doors are heavier than normal doors and have better sealing to minimize air gaps. As for windows, acoustic glass is the way to go. It consists of two or more layers of laminated glass with a special sound absorbent PVB interlayer. When connecting two insulated rooms, we use windows of different thicknesses, ensuring that each window has a different resonance frequency.
Unless you’re planning on suffocating, ventilation is essential in an acoustic bunker. However, this necessarily creates a gap in the construction. Silent ventilators are one thing, but the other solution is the creation of a sound maze in the ducts and vents themselves. These are a combination of acoustic foam to kill the sound waves and plywood dividers that ensure that no sound waves actually reach the room. In order to keep the noise in or out, a certain length of a well insulated sound maze must be accomplished; the rule of thumb says half of the wavelength with some additional corners to break up the sound.
Happy sound insulating!