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You want to soundproof that wall so that you can play your favorite music and movies without having to worry about complaints from your neighbors.
While looking for solutions, you may have come across suggestions of using acoustic foam which is easy to install and not too expensive.
But, will acoustic foam soundproof your room?
Before we come to a conclusive answer, there are a few things to understand here.
Soundproofing Vs Sound Absorption
Many people confuse soundproofing with sound absorption. On the contrary, the two are entirely different.
Soundproofing is basically anything to do with noise isolation or in other words, minimizing sound from entering or leaving an enclosed area.
Sound absorption, on the other hand, is to do with acoustics or rather minimizing reflections inside an area for better sound quality.
So, by ‘acoustic’ foam, what is meant is that the foam is designed for sound absorption thereby improving the acoustics in a room.
Does this mean that a good sound absorbing material would not be a good soundproofing material?
To give you an example, drywall is good for soundproofing and helps in sound absorption as well.
What is a Good Soundproofing Material
Whenever you want to soundproof a room, there are four criteria that must be met for good results.
The four elements on soundproofing are described in detail on Ted White’s website and we will discuss that a bit later. By the way, Ted White is a renowned soundproofing expert and is considered an authority for soundproofing advice on Avsforum.
Here, when we want to define what a good soundproofing material is, MASS is the element to consider.
As brought out by Ted White, for sound to travel through a surface, it has to actually ‘move it ever so slightly’. Sound waves cause a surface to vibrate and it is this vibration that causes transfer of sound through walls, ceilings and floors.
A heavy wall would be difficult to move and hence, would be more soundproof than a wall made of lighter material. This is true for floors and ceilings as well.
There is one rider to this though. A heavy material will be good for soundproofing provided that it is not a good conductor of sound.
That is why concrete is not good for soundproofing as it is a good conductor of sound.
Will Acoustic Foam Soundproof A Room
Foam is too light. Even the densest of foams will never come close enough to provide any kind of meaningful soundproofing.
And if you are looking to soundproof a theater room, you will need 20 feet thick foam to make a difference, no exaggeration.
Hence, acoustic foam is not suitable for soundproofing applications even though it is a poor conductor of sound.
Acoustic foam is just a type of foam which is designed for sound absorption and will do practically nothing for soundproofing. At most, it would be able to block some high frequencies.
But, for the mid and lower end frequencies, there will be no effect, whatsoever.
The Best Solution for Soundproofing
Before you go into serious soundproofing and spend your money, the first step is to identify what is causing noise to enter or leave your room. Don’t blindly assume that it is from the walls.
If the neighbor’s apartment is on the other side of the wall, you will have to check his room too. Check whether sound is getting transferred from air vents, cracks or gaps in the doors.
Compare your room with a fish tank. Any leak in the fish tank will let all the water out. Similarly, in a room, any leak will let all the sound out and let in sound from outside.
After you have checked everything, sealed all places where sound can possibly leak, then only go about soundproofing. This step is very important.
The best way to soundproof a wall or a ceiling is by adding a layer of good soundproofing material while incorporating the four elements of soundproofing. Here they are once again.
Let us assume that we want to soundproof a wall.
This may be a little confusing to a newbie. Decoupling is basically not connecting the studs directly to the walls.
In the figure below by Brighton Soundproofing Ltd, a resilient channel is used to limit the contact points between the studs and the drywall.
With this, the sound that is transferred from the inside wall of the room to the stud and beyond is less.
Insulation would be required between the studs or else the hollow cavities will create resonance.
However, the insulating material should be loose enough to dissipate sound energy. If it is dense, it will transfer sound from the inner wall to the outer wall.
Hence, foam is not a good insulating material for soundproofing either. The best would be fiberglass, rockwool or cellulose of medium density.
Sheetrock, OSB and MDF are some of the best materials for soundproofing as they have a lot of mass. The most popular is sheetrock or drywall as it is cost effective, easy to maintain and has good acoustic properties as well.
The drywall that you attach will also vibrate when sound waves strike it. By adding another layer of drywall with a damping compound sandwiched in between, you can limit the walls from vibrating.
The extra layer of drywall would also add to the mass thereby improving the amount of soundproofing.
I would advise anybody who is thinking of soundproofing, not to waste money on foam.
And, just to reiterate, acoustic foam has not the same as noise isolation foam.
Soundproofing a room or a house is not an easy task. Outsourcing would be expensive and DIY is risky if you are not sure what you are doing.
The basics of soundproofing have been covered in this post. In case you like to go DIY, I would recommend the master soundproofing thread at avsforum.