Soundproofing: Does it really work?

Living in a home with noisy neighbors, on a noisy street, with a construction site nearby, etc., can be an extremely unsatisfying experience, but is there something you can do about it besides buying a pair of earplugs?

In this article, I will be going over what soundproofing is, if it works, how it differs from acoustic treatment, what STC, or Sound transmission class is, the different STC ratings for various materials used in soundproofing, and more.

Without any further ado, let’s get started!

Table of Contents

Soundproofing vs Sound absorption

Soundproofing is the process of isolating or blocking the sound, not allowing it to enter or leave a room.

To do this you will need to use materials that are designed to not let sound through, like drywall.

Sound Absorption 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 at soundproofing, will 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 effective is soundproofing, does it really work?

Proper soundproofing can make it so that even a highway right beside your windows won’t be heard, but this requires high-quality insulation to be installed during the construction process, high-quality double- or even triple-pane windows, weatherstripping, and more.

The question we should be asking, however, is how effective soundproofing an already built home, room, ceiling, door, etc. is, especially if we want to do it in an affordable way without having to tear open half the walls.

I would recommend finding out first where noise is coming in and trying to seal all those gaps with weatherstripping tape or acoustic caulk (generally used for soundproofing windows and doors).

That should already help you quite a bit.

However, if you need to soundproof even further, say a wall, ceiling, floor, etc., then you may need to fork out some extra cash since this will require you installing some drywall, double- or triple pane windows, etc.

Does soundproofing keep noise out?

Soundproofing is designed to keep noise from coming in as well as getting out by using materials that block it, be it because they have a lot of mass, because they cover every single hole where sound can get in or out, etc., and it basically works both ways.

Now, soundproofing helps to keep outside noise from coming in, but you have to do it properly, which is actually the hardest part.

Sound, just like heat, can get in or out through the smallest of cracks, which means that everything needs to be completely sealed off, otherwise it won’t work nearly as well.

You can test this out for yourself: Shut a window or a door completely and then open it just a little. The difference in noise will be massive.

However, if you open the door all the way, more sound will be able to get in, but it’s definitely not proportional and the biggest difference you will notice is between the closed- and slightly opened door/window.

What about soundproofing/acoustic foam panels, do they work?

Acoustic panels are designed to treat the room’s acoustics, or in other words, how sound behaves inside of the room (go back to the top to read the difference between soundproofing and acoustic treatment, since acoustic foam panels are designed for acoustic treatment).

When there’s a sound generated within the room, those soundwaves bounce all over the walls, ceiling and floor, which is known as reverberation (or you could call it echo if you’d like), but without any acoustic treatment or soft materials that can absorb those soundwaves, they will take quite a long time to die out.

Acoustic panels, no matter what they’re made of, are designed to make those soundwaves die down quicker, making the room “feel” quieter because they can’t bounce around for too long before getting absorbed.

As far as actually soundproofing goes, however, they won’t help at all because they don’t block the sound, which means that outside noise will still be able to get in, or any noise from the inside will be able to get out.

So, whenever someone recommends you to get acoustic foam panels installed in your room to keep outside noise from getting in, don’t do it, it doesn’t work.

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:

STC	What can be heard
25	Normal speech can be understood
30	Loud speech can be understood
35	Loud speech audible but not intelligible
40	Loud speech audible as a murmur
45	Loud speech heard but not audible
50	Loud 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.

STC Rating of materials

Here I will be going over which type of insulation material works best when put inside a typical interior wall with ½” of drywall on either side, which has an STC rating of 34 on its own, and how it increases this rating:

Material	STC
Mineral Wool	45
Fiberglass	39
Cellulose	44
Spray Foam	39 for open cell 37 for closed cell

Now let’s take a look at the STC Rating of Window glass, drywalls with and without studs as well as with and without insulation, and lastly floor underlayments:

STC Rating of Window Glass

Single pane glass	27
Dual pane glass	29
Soundproof Window over a single pane window	48
Soundproof Window over a dual pane window	48

STC Rating of Drywall

33	Single layer of 1/2″ drywall on each side, wood studs, no insulation (typical interior wall)
39	Single layer of 1/2″ drywall on each side, wood studs, fiberglass insulation
45	Double layer of 1/2″ drywall on each side, wood studs, batt insulation in wall
46	Single layer of 1/2″ drywall, glued to 6″ lightweight concrete block wall, painted both sides
54	Single layer of 1/2″ drywall, glued to 8″ dense concrete block wall, painted both sides
55	Double layer of 1/2″ drywall on each side, on staggered wood stud wall, batt insulation in wall
59	Double layer of 1/2″ drywall on each side, on wood stud wall, resilient channels on one side, batt insulation
63	Double layer of 1/2″ drywall on each side, on double wood/metal stud walls (spaced 1″ apart), double batt insulation

STC Rating for floor underlayment

Floor Underlayment (under laminate flooring)

Different Types of Noises

There are two types of sound that you should mainly be worrying about:

Air-Borne Noise: These are the sounds that travel through the air, and if there are and gaps or cracks between the walls, doors, windows, etc. this kind of noise will have a very easy time getting in or out.

Examples of air-borne noises are; TV, people talking, music playing, the noise your garage tools make, etc.

Structural Noise: These types of sounds are created when an object hits another one and the vibrations generated travel through said objects like walls, ceilings, floors, etc.

Examples of structure-borne noise are; Footsteps, objects hitting the floor, machinery that vibrates against the floor or against the work table, etc.

How to Eliminate them?

For Air-Borne Noise you mainly need to stop it from leaking out, which means sealing every gap and crack you can find.

For Structural Noise you need to absorb the vibrations that are being allowed to spread through the structures using anti-vibration materials, adding mass (like installing drywall), 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:

Conclusion

Soundproofing can be a lifesaver when you have noise neighbors, if you live on a loud street, if there’s a construction site nearby, etc., and it really does work.

The difficult part about it is soundproofing an already existing home since proper soundproofing is always done during construction.

Otherwise, you may need to add a couple of sheets of drywall on top of your existing walls, replace your windows it double-pane windows (and get a professional to install those), and all of this will cost you quite a lot of money.

Last Updated on May 11, 2022 by Facundo