Does acoustic foam block outside noise?

You see so many pictures of homes, music studios, rooms, etc., covered in acoustic foam and you think “hey, I’m going to get me some acoustic foam panels so that I don’t have to hear my neighbors all day”, or maybe you live on a busy street and want to reduce the outside noise from coming in.

Well, don’t do it. Acoustic foam won’t help at all in this case since it’s designed to absorb sound, not block it, and what you need is to keep the noise out, not let it in and absorb it then.

In this article, I will go over if acoustic foam panels can actually block noise, what other alternatives there are for soundproofing, what better alternatives there are for acoustically treating a room, and much more.

So, without any further ado, let’s get started!

Does acoustic foam block outside noise?

Acoustic foam is soft and lightweight with an open and flexible cell structure that acts as a natural soundwave absorber, preventing noises from bouncing off of hard surfaces, like walls and ceilings, reducing the reverberation present in a room, but it’s not an effective solution for blocking sound and won’t help reduce outside noise.

To be able to effectively lower how much outside noise is allowed in, you need to use thick and rigid materials that block it, not absorb it, such as drywall, for example.

Sadly, there’s a lot of misinformation going around about acoustic foam and how it “should” be used to isolate you from the outside world, but that’s just not the case.

Acoustic foam is used for acoustic treatment, not for soundproofing. Here’s how they differ:

What is the difference between soundproofing and acoustic treatment?

Soundproofing is the process of isolating or blocking the sound, not allowing it to enter or to leave a room. To do this you will need to use materials that are designed to not let sound through, like drywall.

Sound Absorption, on the other hand, relies on materials that are good at absorbing sound, such as acoustic panels, acoustic blankets, etc. to reduce the echo inside of a room.

Sound absorption, while not being great for soundproofing purposes, may still help with it, which is why you might want to use it in conjunction with sound-blocking materials to achieve the best results.

You can learn more about the differences between soundproofing and acoustic treatment here.

How acoustic foam works

Acoustic foam is soft and lightweight with an open and flexible cell structure that acts as a natural soundwave absorber, preventing noises from bouncing off of hard surfaces, like walls and ceilings, reducing the reverberation (or echo) in a room by converting the sound energy into heat.

This is why you usually see music studios with walls covered in high-quality acoustic foam, or any other type of sound absorbing material like rockwool or fiberglass, since it keeps the soundwaves from bouncing all over the place and makes them die down quicker, improving the acoustics in that room.

There are different kinds of acoustic foam, some softer and lighter, some denser and with a cell structure that isn’t as open. The difference lies in how much sound they will allow to pass through; The lighter and less dense the foam is, the more sound it will allow to pass through it.

Now, acoustic foam isn’t that great at blocking sound, which is why it doesn’t work for soundproofing.

It’s worth mentioning that acoustic foam can be extremely flammable, so take that into account when thinking about installing it in your home. My recommendation would be to go with something like rockwool instead.

Reverberation in a room & how it affects you

Reverberation is also what’s known as the “room’s sound”, or in other words, how sound behaves in said room. For example; a large room without any sound absorbing material in it will have a lot of reverberation time because those soundwaves are not being absorbed, meaning that they can bounce off all the walls multiple times.

It’s basically the way a completely empty room feels compared to one that has a couch, curtains, some pillows, and any other material capable of absorbing sound.

Rooms with a lot of reverberation will feel louder, because as I already stated, those soundwaves won’t die down for a long time. Installing acoustic panels, acoustic foam, etc. in this case will make the room quieter, just not from outside noise. If you want to lower the amount of noise that’s able to get in from the outside, then you need sound-blocking materials.

Acoustic foam alternatives that work better

I would recommend rockwool over acoustic foam 99% of the times, and not just because it works better for absorbing sound, but because it’s not flammable, making your home safer.

Of course, I understand that the benefit of acoustic foam is that you can buy the panels on Amazon and simply glue them to your wall, and that’s it! No extra steps required.

With rockwool, or fiberglass, you’ll need to build a wooden frame and cover the insulation material with some sort of fabric, which is a bit more expensive and a lot more work.

Still, always go for rockwool, or at least fiberglass, even though there are some health risks associated with fiberglass, but try and avoid acoustic foam.

Just as a sidenote, the typical acoustic foam panels you see can only absorb really high frequencies, but not the low mids or bass frequencies, which are generally the ones that create the most problems (another reason to go with thick rockwool panels).

Will acoustic foam help with noisy neighbors?

Since acoustic foam is only designed to absorb sound and not to block it, especially the higher frequencies, covering a party wall with them won’t reduce the noise coming from your neighbor’s house. To achieve this, you’ll need to install sound-blocking materials, such as drywall.

How to properly soundproof & what materials to use

Soundproofing is all about blocking sound, not absorbing it, and to do that you need to seal every single gap where air, and therefore sound, can get in or out, and use materials that are capable of blocking the highest amount of sound possible, such as drywall, mass loaded vinyl, etc.

I wrote multiple guides on how to soundproof specific parts of your home, so check those out if you’re interested in learning how to do it:

Generally speaking, the most important step is to first seal off every nook and cranny you can find with weatherstripping tape and acoustic caulk.

Once you’ve done that, and if you’re still not happy with the results, you can more on to the next step which would be installing sound-blocking materials.

This is usually done during the construction phase of your home, since most of the insulation material goes inside of the walls, ceilings, and floors themselves, but if you need to insulate further you could do so by putting up some drywall, installing mass loaded vinyl behind that drywall (careful, it’s really heavy), using mass loaded vinyl as a floor underlayment, etc.

Just check out the guides I linked earlier since they go over all those steps in great detail.

If you want to learn more about how soundproofing works, what the best materials are, the different STC rating of materials used when soundproofing, and more, then read this article I wrote (I’m not going into much more detail in this article since it doesn’t pertain, but it’s really useful to know what materials block the highest amount of noise and in what combination they do so, their STC rating, and more).

Note: I just mentioned the STC rating, which probably left you scratching your head wondering what it actually is.

So, here’s a quick explanation on what it represents as well as what the different ratings mean!

What is the STC Rating?

STC, or Sound transmission class, is the rating used in the US to describe how well a building partition can attenuate sound, such as interior partitions, ceilings, floors, doors, windows, etc.

In most other countries, the Sound Reduction index is used (SRI).

The STC rating reflects the decibel reduction of noise that a partition can provide, where a higher number, or rating, equals better results, or overall attenuation.

Here’s a table showing what each STC rating represents:

STCWhat can be heard
25Normal speech can be understood
30Loud speech can be understood
35Loud speech audible but not intelligible
40Loud speech audible as a murmur
45Loud speech heard but not audible
50Loud sounds faintly heard
60+Good soundproofing; most sounds do not disturb neighboring residents.

There are multiple factors that go into calculating the STC rating, such as the acoustic medium, mass, sound absorption, and more, of the materials, but I won’t go into too much detail about this since it doesn’t pertain to the article itself.


Acoustic foam should never be used if your intention is to block outside noise. Filling up a wall with acoustic panels won’t do anything in this regard, it will just make the sounds inside of the room die out faster, but outside noises will still be able to get in without any problem.

In order to keep outside noises down in a room or a home, you need to use materials that block sound, not absorb it, such as drywall, mass loaded vinyl, etc.

Sound absorbing materials can be used in conjunction with sound blocking materials. For example, putting a sheet of drywall on each side of a wood frame will reduce the amount of sound that is allowed through, but you could also put some rockwool in that frame, making sure to leave no open gaps, and then put on the drywall.

This will reduce noise even further.

Last Updated on May 11, 2022 by Facundo

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