Soundproofing Air Vents (5 Simple Ways to Reduce Noise)

If you’re anything like me, you probably hate doing things halfway. However, when it comes to soundproofing, your projects will actually be unsuccessful if you don’t cover all your bases. 

Well, like windows and doors, air vents are just one more way for noise to get into a room. So if you’re already working on soundproofing a room, you’re going to want to pay special attention to soundproofing the air vents as well.

Really, this is the one area of the room you don’t want to miss. After all, what’s the use of having thick insulated walls if you have those gaping holes in the walls letting in every little sound. 

And, if you’re a musician (or just someone who likes to watch movies with the volume all the way up) you’re also going to want to prevent sounds from going out. Clearly, that’s not possible with regular air vents.

How to soundproof an air vent. Cover it and get the highest noise reduction.

So today, I’ve compiled a list of ways to improve this area of our rooms. Whether you want to get rid of the ventilation entirely or you still want to have some airflow, there are several ways to achieve both results

Best of all, you can use these techniques with any other soundproofing methods you decide to implement. But before we talk about the ways you can soundproof your air vents, let’s answer the obvious question.

Can You Soundproof the Vent without Impeding Airflow?

To answer this question in a word: no. You can’t really expect to install any soundproofing materials over your air vents without them messing with the airflow. After all, the more open you leave that space, the more noise will be able to get in. And the more you try to close the space off, the quieter it will be.

Even the methods that are meant to keep the air going in and out of the room are going to obstruct the airflow a bit. Most of the noise we hear on a daily basis is airborne. So, as you can imagine, that means that we’re actually trying to reduce airflow.

Still, depending on your preferences and soundproofing goals, you may even want to close the vent entirely. As with any other soundproofing project, the most important thing you can do is determine exactly what you want to accomplish. Ideally, you’d find the middle ground between your audio needs and the needs of the room.

For example, if you want the room to be completely silent, the best option would be to close the vent hole. However, if the room only has one window, it would need that extra airflow coming from the vent. So you’d need a solution that reduces the noise coming through the vent but still lets the air come through. But, naturally, that’s easier said than done.

This compromise is incredibly important, especially when we’re talking about airflow vs. quiet. One isn’t better than the other. Obviously, I’m a firm believer in the fact that a quiet home is a happy one. But I also believe in the power of fresh air, so you really shouldn’t have to sacrifice one for the other.

INSPECT THE AIR VENT

Once you know what you want from the space you’re working on, choosing the method you want to implement will be easy. But how do you start preparing the room with the vent for the work you’re about to do? Well, it’s pretty simple.

To begin with, you’ll want to clear away the area surrounding the vent. If it’s high up on the wall or on the ceiling, get a ladder. If it’s lower down, make yourself comfortable on the floor. You can even grab a pillow to kneel on if you think you’ll be working on it for a long time.

You’ll likely see a metal grate over the vent, so you’ll also need your screwdriver or a drill with the appropriate bits to take out the screws. Once you remove the grill, you can check out the inside of the vent with a flashlight. Although, you can also take a peek through the grate.

  • Do Air Vents Amplify Noise?

So, what are some of the things you might see in there that might lead you to conclude that your air vent is letting in more noise than it should? Well, there are THREE MAIN REASON FOR NOISY VENTS:

  • The shape of the duct connecting vents in two different rooms to each other is enabling the passage of sound. Usually, this happens if the vents are straight across from each other, so the sound doesn’t have to turn any corners on its way between the two rooms.
  • Another factor in this equation is the number of walls the sound is bouncing off of. If there aren’t enough obstacles inside the duct, the sound isn’t getting disrupted. Unlike the previous point, this one is pretty easy to solve, as you’ll see later on in this article.
  • Lastly, most air vents are loud simply because they’re not made of particularly absorbent materials. Of course, metal isn’t the best material to use if you’re looking for sound dampening.

So when you’re looking at your vent, pay attention to any potential problem areas. Does the duct bend between the vents in various rooms or is it a straight path between them? Is it metal or does it have a sound dampening layer inside? Finally, how many obstacles do you see in the vent and duct?

These questions are going to tell you exactly what’s missing from your air vent and even how to fix it. From here on out, this is going to be a pretty common-sense type of project. Still, let’s go through some ideas on how you can reduce the noise coming through your air vents.

Inspecting air vents before soundproofing them.

How to Soundproof an Air Vent (Guide)

Because the easiest and most effective solutions to stop noise from coming through air vents involve closing off the holes entirely, I’ll start by suggesting 3 ways to do that. These range from permanently blocking off the vent to using temporary and removable measures. And, after I tell you about those, we can discuss some of the methods that will still allow air to pass through the vent. So let’s get into it.

1. Block Off the Air Vent Entirely with Drywall

The first thing you can do to seal the vent off permanently is to treat it like a wall. You can either fill the duct entirely or just put in wooden studs at the very beginning of the duct, after you remove the grate. Then, you can stuff it with insulation or just close it off with drywall. Finally, you’ll seal the area around your piece of drywall with wall base adhesive to make it blend in.

After everything dries, you can sand the area and wipe it clean, then paint it to match the wall. As you can see from the video below, this technique is very clean and effective — and pretty easy to do as well. However, if you don’t have that much of a budget at your disposal, I recommend trying one of the other tips.

Of course, the simpler and sloppier version of this technique is to flatten the grate and stuff it with gypsum directly. After you’ve plastered over the grate, you can proceed like they did in the video, smoothing the plaster until it blends in. Although I’ve actually seen some people use this method successfully, I’d much rather do a job correctly the first time around. But if you’d rather just get it over with, this is one way to do it.

A word to the wise, though: you’re only going to want to do this if the air conditioning isn’t active. If the AC is actively working through the ventilation system, it will cause condensation to gather. So, in that case, you can adapt this method by using waterproof materials or putting a waterproof tarp before the studs and insulation.

2. Fill the Opening With a Soundproofing Sealant

If you want similar results to the ones you’d get with drywall and gypsum, you can look into using acoustic sealant to plug your vent. Now, I’m not talking about the acoustic caulk you’d use to seal the cracks around your windows. Instead, something like the Great Stuff Big Gap Filler would do nicely.

This product is a foam sealant, so it actually expands to fill the surface you’ve applied it to. Once it sets, it’ll be airtight and water resistant. Additionally, you’ll also be able to sand it to fit into the rest of the wall and paint on top of it.

If you intend to fill the whole duct with this product, you can do so. However, you ought to get enough of the insulation foam to fill the volume of the space you’re working with.

Before you get to work, make sure your gloves are on. You can then remove the vent covers on both sides of the duct if you’re planning to fill the entire space. Then you can fill the space and even put the vent grates back on to keep your room looking as it did before. The whole project should take only a few minutes to apply and a few minutes to set and cure.

On the other hand, you can also only fill the space near the vent itself. Since the product is water resistant, it should be able to withstand the condensation a working ventilation system might generate. So you can also put the foam in and blend it into the wall or even plaster over it to get the right consistency.

3. Cover the Vent With Soundproof Curtains or Blankets

Of course, one of the easiest ways to soundproof your air vents is to cover them with soundproof blankets or curtains. I’ve already written about just how magical both of these products are. Essentially, they’re thicker and more densely woven than regular blankets or curtains (although a regular thick blanket will work in a pinch).

While all of these tips would be easier to apply to wall vents, you could even do them for ceiling air vents. If you’re installing a regular soundproof or moving blanket, you can nail it to the wall or ceiling. However, grommeted blankets would be easier to hang like curtains.

Or, you can save yourself the hassle and just get the soundproof curtains. Install a curtain rod on the wall above the vent or along the ceiling and hang the curtain, making sure that it’s pooling on the floor. This will ensure that you’re fully covered — and it would thicken up your walls as well. Still, I’d use this tip with one of the following two air vent soundproofing methods.

4. Make a Sound Maze Inside of the Vent

There are plenty of reasons why you might want or even need to keep new air flowing into the room. The most obvious reasons why you might need the extra airflow is if the room itself only has a single small window. However, if there’s a possibility of mold growth in the room, you will definitely need to keep the vent functional. And, of course, you can also use this technique for your own reasons as well.

If you’ve never heard about the maze method before, this might seem a bit crazy. But stay with me. Creating a maze inside your vent is a great way to add absorbent materials and walls for the sounds to bounce off of.

You’ll attach these walls to the sides of the duct so that the air is forced to move in a zig-zag motion. This, of course, will force the sound waves to bounce multiple times, which will make them lose momentum and dissipate more quickly. Because the air will still be able to get through, this method would result in the room having sufficient air flow. However, you’d still have a significant noise reduction.

Materials You’ll Need

If you’d like to try this technique out, you can start by collecting the tools you’ll need. After all, being prepared is half the battle. So if you want to set yourself up for success, you can get:

  • A step ladder, if your vent is high up on the wall or even on the ceiling.
  • A screwdriver or a drill with the correct bits. You’ll be using those to unscrew the grate of the vent.
  • A wood saw or a jigsaw to cut the boards with.
  • Thin plywood that’s half an inch thick at most. You can cut several boards to be a bit narrower than the width of the duct. They also need to be a bit longer than half the height of the duct.
  • Adhesive, such as the Gorilla Wood Glue.
  • Thin acoustic foam — so not the one you’d use on your walls. Instead, you’ll want to use a thinner alternative, such as the one Silverstone makes. Their product is only 0.15-inch thick, so it won’t take up too much space in the vent.
  • A utility knife or scissors to cut the foam with.
  • A ruler or another measuring tool.

Finally, you’ll also want to make sure that you have a workstation. If you have had experiences with home projects like this one, you may be able to use the saw without damaging another surface. However, it’s always a smart idea to cover your bases.

Sound maze for soundproofing vents.

Step-By-Step Instructions for Creating a Sound Maze

  • STEP 1

Once you have all of your materials, you can prepare the maze walls. As I’ve previously mentioned, they should be narrower but as tall as your duct. So you can use your measuring tape to measure the dimensions of the duct, then transfer them to the plywood.

After you’ve cut the first piece, check if it fits into the duct. If it does, you can cut the rest of the plywood to that size. The more boards you make, the more obstacles the sound waves will run into.

  • STEP 2

Glue your thin acoustic foam to the boards with the wood adhesive. You can cut the foam down to size before you glue it on or trim off the excess after it’s on the board.

  • STEP 3

Now that you have your maze walls, you can open the vent cover or grill. This is where you might need that ladder.

  • STEP 4

The number of wood and foam maze walls you end up with will determine how far into the duct you place your first wall. Use the glue on one or two sides of the plank and position the first one inside the duct, then hold it a bit until the adhesive sets.

  • STEP 5

The next piece you position will be on the opposite side of the duct. So if you glued the first wall on the left side of the duct, you can put the next in the right corner. That would give the maze that zig-zag pattern. Leave at least an inch of space between each wall — you can make a tighter maze, but it would impede the airflow more.

  • STEP 6

Finally, put the grill back in place.

5. The DIY Acoustic Foam Method

If you already have pieces of egg crate pattern acoustic foam lying around, you can use them to plug your air vent. Take some 3M spray adhesive and apply it to the flat side of one of the acoustic foam pieces. Then press that piece back to back against another one.

Once the adhesive dries, you can cut the foam to approximately the size of your duct. It’s okay if you end up with a piece that’s a bit larger than the duct. The foam will bend a bit and seal the space.

So, How to Stop Noise From Traveling Through Vents

Hopefully, one of these methods will solve your noisy vent problem. Ultimately, you’ll need to choose the appropriate solution depending on your needs and the needs of the room.

If you’re not really using the vent anymore, it’s best to cover it entirely. However, if you still need the airflow, you can use one of the last few techniques to get the quiet room of your dreams.

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