5 Simple Ways of Soundproofing Existing Walls

There is nothing more annoying than trying to get some peace and quiet, only to get disturbed by loud noises from the next door neighbor.

This is when you wonder whether there is a cheap way of soundproofing existing walls to drown out the noise. The ideal solution is to demolish the partition wall and add more soundproofing materials; but, this isn’t always possible as you might be:

  • A renter, thus unable to remove the walls
  • On low budget
  • Afraid of causing damage to the existing walls
  • Or you’re not keen on dealing with all the mess and the work that’s involved in such projects

Whatever your reason, soundproofing walls without removing drywalls and ruining yourself can be a challenge. Here we’ll learn what can be the best way to soundproof existing walls.

But before we dig further into these methods, let’s take a closer look at the source of noise and the main soundproofing principles.

Determining the Source of Noise

Before you jump into any soundproofing project, take the time to think about the noise that’s bothering you in the first place.

To determine the type of sound traveling through the walls, place your hand on the exact spot where you hear the noise. If you feel vibration, the noise is impact based. If there is no vibration but you still hear the noise, it is airborne based.

How to soundproof an existing wall

Some examples of impact noise include knocks on the door or banging on the wall. Airborne noise is when you can hear the next door neighbor’s TV, voice or music blaring through your walls.

Consider the Main Soundproofing Principles

The truth is, soundproofing isn’t as simple as some people may think. But by following a few key principles based on the physics of sound transmission, along with the right materials and techniques, it is possible to accomplish this task.

Whether it’s for soundproofing walls, floors, or ceilings, the 4 following principles apply:

1. Decoupling

The first principle in reducing unwanted noise is decoupling. Sound is a vibration that travels, especially if it has a direct pathway, like a string between two metal cans. If you cut the string, you’ve decoupled the pathway, thus stopping the sound propagation. 

In a wall, this can be done by adding decoupling materials. Even though decoupling reduces vibration transmission to some extent, it isn’t enough to completely stop the noise from propagating.

Decoupling of wall and ceiling with resilient channel with backer rod at junction

This is why we need to apply more soundproofing principles. Keep reading to learn more…

2. Absorption

Have you ever blown across the top of a bottle and heard a sound? This sound is actually the trapped air reverberating. A hollow wall traps air much like the bottle reverberating the trapped air. When the wall vibrates by the noise your next door neighbor makes, the air in the cavity also vibrates as a result.

Sound absorbing materials are usually used in wall cavities as much as in ceilings.

Fiberglass insulation in wall and ceiling cavities

So even though the wall is decoupled, there is still the vibrating air in the wall cavity that will transmit some noise. To absorb this sound, you’ll need insulation materials like low-density cellulose… more about that later.

3. Sound Blocking

Any thick or heavy object you install in your wall will block sound. Adding mass is important in reducing noise, and one of the most inexpensive sources of mass is drywall. Using two layers will ensure your wall won’t vibrate.

4. Damping

Tap a glass with a fork and you’ll hear a ringing sound. Now tap it with your finger; the ringing sound will stop right away. This is what’s known as the damping effect.

Sound damping a bell

In soundproofing, liquid, waterborne damping compounds made of viscoelastic adhesive are effective noiseproofing products. If you want to know more, scroll down the article and read about how to seal the gaps in your walls using noiseproofing adhesive.    

Which Principles to use?

While the four soundproofing principles I’ve talked about work independently, use all four for best results. For example, if you are applying plenty of mass to your walls but without damping, your soundproofing effort will be weak.

Here are several easy and inexpensive techniques you can use to soundproof your existing interior walls to reduce both impact and airborne noise.

5 Ways of Soundproofing Existing Walls

1. Fill the Gaps with Acoustical Sealant

Sound can escape through the smallest spaces. By sealing up the holes or cracks in the corners of the existing walls, it can make a big difference in reducing both impact and airborne noise.

I prefer using a damping compound like Green Glue to fill the gaps.

This acoustical sealant makes walls more air-tight and as a result, it’ll be more difficult for the soundwaves to travel through the walls.

When used in combination with the other soundproofing techniques we’re about to discuss, it will dampen noise to a great extent.

Green Glue damping compound for soundproofing offices

2. Install Extra Drywall

To apply the sound blocking principle to your existing walls, add extra drywall. A double layer of drywall will separate the main wall and allow sound to bounce off the new drywall before hitting the main wall.

Drywall ready to be installed on a wall (soundproofing existing walls)

This sound-deadening method is very easy to apply. But before installing the double-layer drywall on the existing wall, I recommend that you apply a layer of noise soundproofing compound on top of the wall, then secure the new drywall using screws to attach the panel to the studs. Once you’ve installed the drywall, use an acoustic caulk to seal any gaps along the drywall panels.

3. Apply Blown-in Insulation

Ok I admit; this soundproofing technique is more expensive and time-consuming than the other methods. But it does work well in reducing soundwaves amplitude. The idea here is to use the sound absorption principle in your walls to deaden sound.

Blown-in insulation, as the name suggests, is a foam-like material that’s blown in the walls using a blower machine. This type of insulation is made of low-density cellulose and loose in nature. It works by trapping the air pockets and reducing echoes created from airborne noise. Cellulose is a non-toxic sound absorbing material that’s recycled and treated to make it fireproof.

Another common insulation material is fiberglass. Its advantage is that it dries immediately once blown in the walls.

It may be wiser to hire a professional insulation installer to do the task for you. But if you’re not keen on spending an extra $15 per square foot for labor charges, then watch the demo video below:

4. Opt for Mass Loaded Vinyl

Mass loaded vinyl, or MLV for short, is an extremely dense, but thin rubberlike material. It is commonly used for soundproofing applications. This flexible, environmentally-friendly vinyl material acts as an extra layer on your wall. It gives the wall extra mass to improve its sound blocking efficiency.

MLV will prevent both sound waves and vibrations from traveling through your walls.

Mass Loaded Vinyl for office soundproofing

How to install mass loaded vinyl? Hang your double layer drywall over the MLV in a vertical or horizontal manner. Seal the seams using the acoustical sealant before mudding the drywall seams and finishing the wall to your desired results.

5. What if the Existing Wall is not Made of Drywall?

In older buildings, you’re less likely to find the existing wall made of drywall. While this is actually a good thing as the wall material tends to be heavier and more resistant to vibration sounds, it doesn’t mean it is completely soundproof.

Let’s look at how to soundproof walls that aren’t made of drywall:

Brick walls: bricks are dense materials that have a good sound blocking capability. But they lack sound absorption. To improve their sound-absorbing ability, install acoustic isolation tiles on the brick walls. These tiles are more powerful than the traditional acoustic panels, plus you can glue them to the wall without using any other tools.

Plaster walls: plaster is already a great sound stopper. But if your existing walls are made of plaster and not meeting your soundproofing needs, consider making improvements to them. Follow these quick steps:

  1. Begin by sealing any gaps or holes in the plaster with Green Glue.
  2. Next, install MLV to the wall before adding a layer of drywall.
  3. To finish, apply mud to the drywall before priming and painting.

Summary

The above mentioned techniques are some effective ways to soundproof your existing walls as a DIY project. These budget-friendly soundproofing methods work on eliminating both impact and airborne sounds. But to achieve the best result, I recommend using a combination of these techniques for utmost success.

I hope these few tips will help you find a better sleep at night or make peace with your neighbor.

Peace & Zen-Up!

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Ludovic
Ludovic
Ludovic uses his technical experience as a Mechanical Engineer to compile Soundproofing DIY guides. You’ll often find him breaking down complex topics to make it clearer for others. He also finds inspiration in sharing mindful habits.

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