On Soundproofing and Acoustic Foam: Facts and misconceptions

Acoustic foam is among the most popular products used for soundproofing purposes. Yet, it seems that the purpose of acoustic foam has been misunderstood. There are many misconceptions about soundproofing and acoustic foam, so let’s find out what’s true and what’s not.

Sound Proofing vs Sound Absorption

The main reason why people usually think of acoustic foam is because they don’t know the difference between soundproofing and sound absorption. It makes sense to assume that if Many people are under the assumption that these two aspects are one and the same. However, this is far from the truth. There is a distinct difference between sound absorption (Open cell foam) and sound blocking (Closed cell foam).

Sound absorption refers to the process where a soundproofing material soaks up the sound, whenever sound waves hit the foam. Such sound will “blow through” open cell foam but not closed cell foam.
Sound proofing (sound blocking) refers to reducing the sound pressure waves passing through from the sound source. The source can be an instrument, a machine, many types of annoying noises, etc.

The primary objective of acoustic foam is to reduce the reverberation or echoes in a room. It can never block sound.

What Soundproofing Requires

Sound does not ‘go’ through a divider or roof but rather just vibrates it. These vibrations are transmitted to the opposite side and that is how sound travels through dividers, roofs and different surfaces.

To achieve good soundproofing, we need material that does not vibrate when struck by sound waves. In order to achieve that, the material needs to be dense and heavy enough to not allow vibration at all. If we take foam as an example, it is neither dense nor heavy and thus does not work for soundproofing.

Here are a few tips about what you should do to soundproof your walls, floors, doors and windows.

Walls and Ceilings

In order to soundproof your walls and ceiling, you can install extra drywall. A 1.5 cm thick drywall sheet weighs about a kg per square foot. This is a low cost-high mass solution. But it requires a lot of effort and workmanship, and involves modification to the room, which those of us who rent cannot do.

Another option can be to install mass loaded vinyl, a flexible piece of material that is also dense and thus good for soundproofing. It’s easy to install, has a very high density and mass and can be removed very easily. The problem is that it can be costly. At $2.5 per square foot on Amazon, it can be expensive to soundproof an entire room.

Floors

When it comes to floors, there are special soundproof underlayment one can use. They usually come at 1cm thick and weigh about 650 grams per square foot. They are easy to install, highly effective but they can get expensive depending on the room size. You can also use Mass Loaded Vinyl, which still has the same pros and cons we discussed earlier.

Doors and windows

Doors are usually weak and light, making easy for sound to pass through them. It is also much harder to soundproof them. The only options available are to either change the door to a heavier denser one, or to have communicating doors. These are a set of two doors with an air gap in between, which helps insulate against sound. You can see an example in the video below.

https://www.youtube.com/watch?time_continue=40&v=OXB1eFZ5p14

When it comes to windows, however, it’s harder. Covering the window with foam panels does not help as we discussed earlier because foam is neither heavy nor dense, Using expanding foam in between the cracks and gaps would help but enough to prevent direct leakage of sound.

The best option to soundproof windows is to have a two layered window with an air gap in between, acting as an insulating layer. You can also simply add another layer of glass and use your existing window as the first layer. The second layer can be acrylic or laminated glass, or better even, acoustically laminated glass. The latter is of course the best option for soundproofing.

Soundproof curtains are a good option for windows too. They are quick and easy to install and don’t cost must but are not as effective as double glazing or window plugs.

Soundproofing is not rocket science. However, there are certain materials that need to be used to block sound. When it comes to “acoustic” foam, we need to understand its purpose, and use it accordingly. Always speak with soundproofing product technicians and get all your queries answered before purchasing a product. This can save you a lot of time and money.