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How To Soundproof A Window AC Unit

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Trading the sweltering weather for a headache? It doesn’t have to be that Way!

When those scorching summer days come around, thank the lord we have window AC units to bring in some sweet, sweet cool air, and save us from a puddly fate, à la the Wicked Witch of the West. But, as I’m sure you know, this breezy relief comes at a cost: peace and quiet. 

Yep, as soon as you fire the old window warrior up, you’re met with a 50dBA racket supplemented by all the noise filtering in from the summer streets — don’t you just love it when solutions create more problems!

To make matters worse, if the sounds in the street are making their way into your abode, then so is all the hot, stifling air, limiting the efficiency of your AC unit.

Not to worry, though, friend. I’m going to share with you some window AC soundproofing techniques that prove you don’t have to trade one evil for another. It may not seem like it right now, but trust me, your living space can be both cool and calm.

How to Soundproof a Window AC Unit

Soundproofing To Block Street Noise

Our first port of call is to tackle all that summer street noise wafting in through the window and ruining your good time. Once we’ve sufficiently silenced the streets, we can focus on the AC unit itself and solve this dBA debacle once and for all!

There are two methods of blocking street noise while using a window AC unit. One is a little trickier than the other, but I’ll cover both, so you’re aware of all your options.

Soundproofing to Block Street Noise — Method 1

Okay, so, basically, our first street soundproofing method is all about recreating the screen that comes with most window AC units, but making it way, way better.

If you’re reading this article, I’m sure you know better than anyone that, while the AC companies get an A+ for effort, the soundproofing screens they provide are suboptimal at best.

They leave lots of little (sometimes not-so-little) gaps along the walls of your AC unit, and this is where the noise pollution works its way in, stoking the worst headache you’ve ever experienced in your whole dang life.

What You’re Going to Need

  • An acrylic sheet – Acrylic has fantastic sound-blocking abilities, and it can be purchased in transparent sheets, which is great, as it means you don’t have to sacrifice light for peace and quiet.

Glass may be a fancier option, but it’s brittle, difficult to cut, and isn’t the best for soundproofing.

  • A ruler – You’ll need this to make accurate cutting guides
  • A pencil – For marking the acrylic.
  • Poly tubing – You’ll be using this to line your acrylic cut out.
  • A large piece of scrap plywood – This will give you something to rest the acrylic on when cutting. It doesn’t have to be plywood. Any sort of supportive surface that won’t blunt your knife will be just fine.
  • A cutting guide – A straight-cut block of wood will work just fine.

The Process

  1. Use your ruler to measure the dimensions of your AC unit and the width of your window.

You might need to subtract a millimeter or two from all your measurements to account for your poly lining.

  1. Mark your measurements on your acrylic sheet with your ruler and pencil.
  1. Use your plywood (or whatever appropriate surface you have lying around) to rest your acrylic sheet on, then get slicing. Use your straight-cut block of wood as a cutting guide. Your acrylic screen should come out looking like an upside-down U.

If you’re not feeling confident to cut the acrylic yourself, contact an acrylic supplier, give them the measurements, and pay for a professional custom cut.

  1. Test the fit of your acrylic screen around your AC unit. There should be a minuscule gap (for the poly tubing to fill).
  1. Apply your poly tubing to the edges of your acrylic screen the way you’d fit a gasket rope around a stove window.
  1. Slot your acrylic screen in place against your window frame, and voilà; you’re done!

Soundproofing To Block Street Noise — Method 2

This method is all about reinforcing that shoddy screen that came with your AC with some lovely, thick acoustic foam. With the two of these layers working together, no matter how bustling the summer streets become, you’ll feel like the last human on earth — in a good way, of course.

What You’re Going to Need

  • Scissors – A decent pair of scissors will glide through the insulation foam.
  • A ruler – To keep your cutting markings straight.
  • A pencil – To draw your cutting line.
  • Foam weather stripping – This nifty insulation tape will be covering all the tiny gaps between the sound-dampening foam and your window frame/AC unit.

The Process

  1. Use your ruler to measure the left and right gaps between the window frame and your AC unit. You’ll need both the length and the width.
  1. Using your ruler and pencil, mark out the side measurements on your insulating foam. Try to be as economical as possible, so you have some spare for later.
  1. Cut your side panels from the foam, and place them over the fold-out screen that came with your AC unit. Some foams will have an adhesive side, but if yours doesn’t, don’t sweat it. Just add a millimeter or two to your measurements, so it stays put when squeezed into place.
  1. Measure the gap from the left to the right of your window.
  1. Use your pencil to mark this measurement on your remaining foam. This is going to be your horizontal section sitting on top of the lateral panels, running across the top of the AC unit.
  1. Cut your horizontal panel from the foam, then set it in place above the AC unit.
  1. If you have the foam to spare, you can cut another horizontal section for sitting beneath the AC unit as well, if you’d like. I’d also recommend keeping enough foam to cover the vent of your AC unit when not in use. This will help to block any street noise filtering directly through the unit.
  1. Apply your foam weather stripping to any of the small gaps between the foam and either your window frame or your AC unit, and that’s that!

If you’re still not happy with the soundproof qualities of your insulation, just repeat the process, and add another layer.

Soundproof a Window AC Unit

Soundproofing A Window AC Unit

With that messy business taken care of, we can get to work transforming your AC unit’s roar into a purr.

If you feel that your AC unit is louder than it ever was before, your first priority should be checking for possible causes. There’s a good chance a spot of maintenance will bring the running volume down a great deal before you even hit it with any soundproofing (or a baseball bat).

Troubleshooting Your Window AC Unit

  • Double-check your installation.

A lot of the time, excess AC noise will be caused by a loose fit. Check if it’s securely fixed into place, making sure the screws of the included fold-out panels are nice and tight.

  • Look at the fan blades.

As the primary moving components of your AC unit, if the noise has gotten out of hand, the fan blades should be your number one suspect. They might be bent and knocking against another component. Perhaps it’s another component that’s warped and getting in their way.

Give them a look over, dust them, and gently bend them back into place if necessary.

  • Oil the motor.

If your AC unit is a little long in the tooth these days, it’s possible the motor lubricant is spent.

Try applying a couple of drops of oil down the motor shaft. Understandably, you may not be too comfortable doing this, so feel free to consult a professional, and ask them to apply the lubricant for you.

  • Dust and straighten the cooling fins.

These delicate components can normally be found just behind the rear panel of your AC unit. If you can figure out a way to remove the panel, give the fins a very gentle dusting, and straighten them out using a fin comb.

  • Is the noise coming from your windowsill?

Perhaps your AC unit isn’t the one to blame for the racket. Sometimes it’s the way the windowsill amplifying the noise, especially if they’re made from plastic.

This can almost always be solved by fitting foam weather stripping around the frame of your AC unit, reducing vibration transmission. Alternatively, why not try moving the AC unit to a different window?

Diagnosing Your AC With Your Ears

I know it’s the last thing you want to do, but listening closely to the noise your noisy AC unit is making can be a great way of diagnosing the issue.

Popping, Rattling, or Screeching

If you can’t find anything wrong with the fan blades, a popping noise could be caused by liquid refrigerant finding its way into the compressor. 

Rattling or vibrations are also a compressor issue, but a compressor blanket can help with this (more on that in just a sec).

A loud screeching sound is usually a sign that the compressor is dealing with too much pressure. If this is the case, you’ll need to shut it down immediately, for both your own sanity and the wellbeing of the unit.

Compressors can be replaced, but they tend to cost a pretty penny. You might be better off buying a whole new unit.


Other than a misshapen fan blade, the only cause for an irritating clicking noise is an electrical fault, so you’ll need to call a professional in.

Soundproofing Methods For A Window AC Unit

Compressor Blanket

You can think of compressor sound blankets as rubbery tea cozies that sit on the compressor and mute all its mutterings. It’s the same material used to keep cars sounding quiet from the inside.

I’d only recommend using a compressor blanket to stifle rattling or vibrations. Other compressor noises, such as popping or screeching, are symptomatic of more severe issues that need to be addressed immediately.

Sound Barriers

Granted, this isn’t the most space-friendly solution, but it can help. The idea is that you set up a booth around the AC unit with sound barriers.

These barriers could be crafted from sound-dampening curtains on clothes rails, or you could invest in acoustic office-style dividers, although these can be mighty expensive.

Custom Made Rear Sound Guard

In my opinion, a custom-made sound guard is the best solution to a noisy window AC unit. They’re simply a cage with some sort of funnel or opening at the top.

Once fitted to the vent of the AC unit, the cage blocs most of the noise, but the air compressor can still “breathe” through the opening. The bad news is that, unless you’re hot on the DIY front, you’ll have to get the sound guard custom-made, which can be expensive.

How To Prevent AC Noise Issues Developing

There’s no magical method of keeping your window AC unit on top form. It all just comes down to a good care and maintenance routine, so before we go our separate ways, let’s run through a few pro AC TLC tips.

  1. Clean the filter.

It’s good practice to clean your AC filter at least once a month when the hot weather hits. Start by soaking it for a few minutes, then treat it to some spot cleaning, wipe it down, and set it to air dry somewhere safe. If you’re dealing with a particularly funky filter, just replace it.

  1. Coil care.

Coils are situated in the front and rear of your unit. If you can remove the panels, give them a gentle once over with some coil cleaning solution, then wipe them downwards with, rather than against, the orientation of the fins.

  1. Drain the drainage.

Don’t let your drainage pan get too full, as it can stimulate the buildup of condensation within the unit.

  1. Proper Storage.

AC units can get pretty dusty or even damaged if they’re not stored properly, so make sure you box it up and try not to pile tons of things on top of it.

How To Soundproof An AC Unit — Summing Up

We love you, AC units, but good lord can you make a racket! Hopefully, by mixing a couple of the soundproofing solutions in this article, you can survive the summer in relative sanity.

If the headache persists, it might be time to bite the bullet and invest in a more modern unit with advanced, integrated soundproofing technologies. Either that or you can summer in Antarctica, whichever sounds best to you.