The best way to soundproof an existing wall is . . . to tear it down and start from the studs. You'll always get better performance and spend about the same on the project. When soundproofing a wall, here are the things that matter:

• • Add Mass – each time you double the mass of your wall, you increase the STC Rating by 3-5 points.
  • Varying the Materials – you can stop a wider range of frequencies by varying the materials that sound has to travel through, thus improving your wall’s blocking ability.
  • Seal up the Wall – If you have any gaps, cracks, or seams, seal them with acoustical sealant to keep sound from leaking out. Upto 5 STC points depending on how bad it was to begin with.
  • Add Insulation into the Wall – blow-in insulation (not spray foam) is a great way to reduce sound transfer. STC Rating imroved by 3-5 points.
  • Decouple the Wall – sound is just vibrational energy, so by decoupling your new wall from the existing wall, or even studding out a new wall in front of the existing wall, you will greatly reduce the amount of sound that will pass through.

How to Soundproof ANY Wall:

Types of Wall assemblies

There are two types of noise that we deal with when soundproofing a room: airborne noise and structural noise. Walls are prone to airborne noise, which includes loud music, people talking, phones ringing, dogs barking, loud sirens, etc. A wall's ability to block sound is referred to as an STC rating! It depends on factors like wall construction, materials used, and things like the building’s age and the quality of the construction. Here are some examples of what your walls might look like.

While we've stated that removing the drywall is always the best solution, even if you started your research hoping to avoid it. Nevertheless, for this section, we're concentrating on solutions that do not involve removing drywall. If you need higher performance, read our wall soundproofing guide for a more extensive look at how to do right. But let's get to it!

Solutions to Soundproof Existing Walls

When soundproofing of an existing wall, there are a handful of approaches ranging from okay to very good, an it will depend on how much sound you need to block.

Recommended Solution: RSIC-1® Retro Sound Isolation Clips

Alternative Solution: Green Glue + 5/8" Drywall

Alternative Solution: BlocknZorbe™ Sound Panels

Most acoustic panels only absorb sound waves, improving the sound quality and reducing echo and reverb within a room. But they will not stop sound from traveling from one room to another (soundproofing). HOWEVER, as the name suggests, our BlocknZorbe panels are designed to block AND absorb sound.

With 100% coverage of a wall with the 2" thick BlocknZorbe™ you can reduce sound through that wall by 8-10 decibels.

1. Step One: Seal the edges and penetrations of the existing wall with acoustical sealant
   
   
2. Step Two: Screw each panel into the wall or use construction adhesive to adhere them to the wall
   *you MUST cover 100% of the wall for this to be effective at all
   
   
3. Step Three: Seal around the edges and penetrations with acoustical sealant

EXPECTED STC RATING: 40-42

Alternative Solution: Mass Loaded Vinyl + 5/8" Drywall

Mass loaded vinyl is a great soundproofing material because it is super dense, versatile, and great at blocking sound. Best of all, it checks the “varying materials” box. But it’s an industrial product best placed behind drywall.

It also needs the sturdiness of the studs to support its weight, because drywall will NOT support the weight of MLV. However, if you fasten it directly to the studs through the drywall, you can use mass loaded vinyl for existing walls, but again, we recommend direct attachment to the studs.

If you install MLV to the studs through the drywall, we recommend installing a second layer of drywall over the MLV to get that finished look, but at that point, it’s a lot easier and of similar effectiveness to just use Green Glue and a new layer of 5/8” drywall.

EXPECTED STC RATING*: 45-47
*with second layer of drywall

Alternative Solution: Blown In Insulation to Wall Cavity

We felt that we had to comment on blown in insulation as a soundproofing method because so many other websites reference it as a potential solution. The fact is, insulation is an important component of a high-performing wall assembly. But if your wall already has insulation, you won’t improve the wall’s STC rating by blowing in more. In fact, overstuffing the wall with insulation you will reduce the soundproofing of the wall. If your wall does not have insulation, add insulation to reduce the amount of noise through your wall. It is imperative that you well-seal any holes you make to blow insulation in.

For more on insulation and if soundproof insulation works, check out our article on the topic.

EXPECTED STC RATING: 31-33

Other Things to Consider When Soundproofing Existing Walls

Here are a few things to keep in mind when soundproofing an existing wall in your multi-family or office:

Shared Walls May Share a Ceiling Too

In office spaces with shared wall noise issues, you may also share a ceiling. In some constructions, to save on building cost the wall between units can sometimes not go all the way up to the true ceiling. And if you have a dropped ceiling, it's very possible that sound is traveling up over the wall and down into your space and vice versa. Traditional ceiling tiles with some insulation above them won't block sound from passing between spaces.

If that's the case, bring the wall all the way up to the true ceiling for best results. Otherwise, investing in ceiling tile backers will go a very long way toward keeping unwanted noise from traveling over the wall. Don't soundproof your walls if you don't plan on addressing this.

Read our office soundproofing guide for more tips on this.

Soundproofing your Doors is Just as Important as the Wall Itself

If there is a door in the wall that needs soundproofing, you CANNOT neglect it. Doors are almost always weaker sound barriers than the wall around them. Swap any lightweight, hollow core doors for solid core doors, and install a door seal kit for even better results.

Plaster and Brick Walls Are Good Sound Blockers on Their Own. What If That's Not Enough?

Plaster walls, concrete walls (STC 45 - 6" concrete blocks), and brick walls (STC 45 - 4.5" face brick) are all good at blocking airborne noise on their own because they have the mass needed to block it. They all have an STC Rating between 42-48 depending on thickness and composition.

If you need more soundproofing, removing those walls is obviously a chore. Our recommendation is seal up any cracks gaps or seamsto stud out a wall in front of the existing wall, sometimes called, "a room within a room". Fill that cavity with insulation, and close it in with 5/8" thick drywall. Use one of our other wall soundproofing methods to accomplish even greater sound blocking.

Do NOT Use Acoustic Panels to Soundproof Existing Walls

To address the elephant in the room, DO NOT use acoustic panels to soundproof existing walls. Acoustic panels are designed to improve the sound quality of a space, and are not meant for blocking sound. It won't work. Don't do it. If your office needs an acoustic treatment, read our article for help. However, acoustic panels can help to reduce the overall noise inside the room to reduce how much sound is trying to transfer between spaces. It's not ineffective, but it's more of a phase 2 to a good soundproofing plan.