How to Soundproof an Air Conditioner; In 8 Simple Steps!

Air conditioners are essential for our way of life, nobody likes extremely hot or cold weather and air conditioners help with this quite a lot.

However, they are very noisy, especially the older ones.

In this post I will go over how to soundproof both the outdoor and the indoor units, starting with the outdoor one since it will be responsible for most of the noise.

Table of Contents

  1. Use an Acoustic A/C Blanket
  2. Build a Soundproof Box for the A/C
  3. Install Sound Absorbing Materials
  4. Soundproof the doors and the windows
  5. Reduce the Vibration Noise
  6. Stop the Air Conditioner’s flaps from moving
  7. Build a Sound Dampener

Outdoor unit

The outdoor unit will generate the most amount of unwanted noise, and even though it’s outside it can make so much noise that it becomes unbearable.

There are a couple of options you could go for;

1. Use an Acoustic A/C Blanket

The easiest way to soundproof an outdoor A/C unit is by using an acoustic blanket.

Adding an extra barrier that can block and absorb sound will help quite a lot when it comes to reducing the A/C noise.

Soundproofing blankets are excellent at this, especially the ones specifically designed to lower A/C noise.

They are affordable and easy to install, and most of all, they are effective.

Note: Keep in mind that the air conditioner might overheat if it’s working for too long with such a blanket covering it since it will hinder the airflow.

However, because of its sheer simplicity and affordability, I don’t think you could ever go wrong with an acoustic blanket.

This acoustic A/C blanket can fit different models and sizes, that is why it’s my personal recommendation.

Try it out and see if it reduces the sound enough, if you still feel like you need some extra noise reduction, then try the next few steps…

2. Build a Soundproof Box for the A/C

Just like the soundproof boxes used for generators and air compressors, you could build one for your Air Conditioner.

Note: It needs to have some ventilation, otherwise it will overheat and kill the A/C.

How do you build the box?

To do this you are going to need a couple of materials, some of which you probably have laying around in your garage.

You will need Medium Density Fiberboard or anything similar. The thicker the better.

Also make sure to get Mass Loaded Vinyl since this will be the material responsible for sound absorption.

Mass Loaded Vinyl is more commonly used to soundproof a car, but it can work for any soundproofing applications.

Purchase some Acoustic Caulk, since this will allow you to seal all the little cracks and gaps properly.

Also make sure to purchase some screws, nails, L-brackets and a table saw or circular saw.

Important note: This box will work best with A/C units that are standing on the ground, if yours is mounted to the wall you could adapt the box to also be mounted on to the wall.

Step 1: Take Measurements

The first thing you need to do is measure your A/C to make sure that it can fit in the box.

Give it at least one foot of extra room on the top to allow for better airflow.

After you’ve measured every part of the box including side-, front and back panels as well as the top one, it’s time to cut the fiberboard.

Step 2: Cut the Box

Tip: Use a pencil on the fiberboard to trace exactly where you are going to cut, you don’t want to make mistakes here.

Now all you have to do is cut the fiberboard using a saw.

Step 3: Put the box together

Using glue and the L-brackets plus the screws, put the box together as best you can.

If possible, avoid leaving open gaps between the pieces of fiberboard.

Step 4: Make two ventilation holes

As I already mentioned, airflow is essential to keeping the A/C’s motor cool.

Make one hole on the top panel and one on the front or back panel.

Note: The holes should be facing away from where you are trying to keep the sound from reaching.

Step 5: Line the inside of the box with Mass Loaded Vinyl

Cut the MLV and adhere it to the inside of the box using green glue and nails or staples.

It’s important to cover as much surface as possible and to also not leave any gaps between the different pieces of vinyl.

Step 6: Use Acoustic Caulk to seal the gaps

Acoustic caulk will prevent sound from exiting through the gaps left between the vinyl or the MDF.

Recommendation: A generous amount should be applied.

Step 7: Place the box on top of the A/C unit

Lastly, all that’s left to do is to install the box.

If you’re A/C unit is wall-mounted, then a couple of adjustments will be needed.

3. Install Sound Absorbing Materials

How To Reduce Noise From Air Conditioning Unit

High density acoustic foam isn’t really designed to block sound like mass loaded vinyl is, but it can still help absorb a lot of the noise that the A/C unit generates, lowering the overall noise level.

Getting three pieces of this acoustic foam and adhering it to the wall behind the unit can drastically help with lowering the overall noise.

To install it you will only need some glue spray and about 20 seconds of time and you’re done!

If you want to take this step even further, you could install mass loaded vinyl on top of the acoustic foam and then install acoustic foam on top of the vinyl again.

Since MLV is REALLY heavy, adhesive alone won’t cut it. I’d recommend using nails or screws to adhere it properly.

4. Soundproof the doors and the windows

While soundproofing the A/C unit itself may be the most effective and logical option, you really should consider soundproofing the doors and the windows since this is where most of the sound will be able to come in.

Step 1: Weatherstrip the Doors and the Windows

One of the most effective, affordable and quick methods is to apply a weatherstrip which will form an air-tight seal between the frame and the door/window.

You will need to use this weatherstrip and adhere it to the frame while making sure that once the door/window is closed, there are no gaps left open.

Step 2: Seal the gaps with acoustic caulk

You need to get this Acoustic Sealant and using a caulk gun you can begin the installation.

It’s designed to fill small 1/8” gaps to ½” gaps and should be applied between the frames and the wall like little cracks, etc.

Make sure to apply it carefully. Once you’re done you can wipe the excess off with a wet cloth.

Acoustic caulk is designed for interior use only; it shouldn’t be used on the exterior!

Note: After you have applied it, give it about 48hs to dry completely.

Step 3: Install a Door Sweep

This is a very simple step that only takes about 1 minute and can help quite a lot.

A door sweep will essentially cover up the gap that’s left between the door and the floor decreasing the amount of noise allowed in.

This is the door sweep that I’d recommend you get since it’s very affordable and easy to install thanks to its adhesive backing.

Step 4: Install Acoustic Curtains on the Windows

Acoustic curtains, although they aren’t able to block 100% of the noise, are very effective.

You can get them in a variety of colors. This will allow you to use them not just for soundproofing purposes, but also for decoration, since they actually look quite nice.

They should go from ceiling to floor and also a couple of inches past the sides of the window.

If they are wider than the window, then this means that the curtain itself will have more folds which will help seal it off better.

The acoustic curtains that I’d recommend are the NICETOWN blackout soundproofing curtains for the simple fact that considering the price, you won’t get anything better.

These are just some basic steps on how to soundproof the doors and the windows, here are the full guides for both;

5. Reduce the Vibration Noise

The vibrations generated by the A/C can easily be transmitted to the ground or the wall, depending on where it’s mounted, especially if it hasn’t been installed properly.

Check to see if it’s leveled properly and if the screws are as tight as they can be.

If, for example, your A/C is mounted on the outside of your bedroom wall then the vibrations will reverberate and generate a lot of noise inside the bedroom.

Consider changing the A/C’s location and placing it on top of some anti-vibration pads in order to reduce the vibrations transmitted to other structures.

6. Reduce the water dripping noise

This one is very easy to deal with, luckily, since it’s something that annoys me like you wouldn’t believe.

If there’s one sound I don’t like hearing, especially when trying to fall asleep, it’s water dripping.

The way I solved this was by attaching an extra hose to the A/C’s hose and putting it inside of a bottle.

Inner Unit

When it comes to reducing the noise of the indoor unit of an A/C, you mainly have two ways of approaching it;

Step 1: Stop the Air Conditioner’s flaps from moving

The A/C’s flaps tend to generate a lot more unwanted noise than you might realize, so make sure to set the settings in such a way that they stay still.

If this isn’t possible then your best bet would be to read the manual to see how to remove them entirely.

Step 2: Build a Sound Dampener

This won’t completely solve the problem, but it will at least absorb some of the A/C’s sound, making it more manageable.

You will only need some pieces of plywood or medium density fiberboard, acoustic foam and some effort.

It should look something like this;

Image taken from the Auralex University Website


Soundproofing the outdoor unit takes a lot of work, especially when you want to build the soundproof box, which I’d still recommend since it’s well worth it.

I’d recommend you start by purchasing the acoustic blanket and seeing how much of a noise reduction you get.

If it’s still not enough, then consider soundproofing the doors and the windows since this is very cheap to do and also highly effective.

If you follow all of these steps, then the reduction in noise should be significant.

If you know of any other methods for soundproofing an Air conditioner that I didn’t mention, let me know in the comments below.

Last Updated on March 3, 2021 by Facundo

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