How to Soundproof a Window Air Conditioner for Peace and Quiet

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Is your window AC unit keeping you up with its loud humming? Struggling to hear conversations or focus with the racket?

Thankfully, there are several straightforward DIY methods for soundproofing a window air conditioner against noisy exterior sounds or the unit itself.

Let’s dive into the top three solutions for effectively blocking noise from your window mounted AC this summer.

Why Soundproof Your Window AC?

A visual representation of the soundproofing process for a window air conditioner. The image showcases a serene room with a window AC unit, now soundproofed, allowing for quiet operation. The journey from a noisy compressor and fan motor to a tranquil space is reflected in this illustration.

There are several benefits gained by taking steps to soundproof your window air conditioning unit:

Reduce Noise from the Compressor and Fan Motor

The internal components of a window AC unit generate significant noise when operating. The compressor circulates refrigerant through the AC system with a constant pumping hum.

Meanwhile, the fan motor spins the blower to push air across the cold evaporator coils and out the front of the unit.

Together, the sounds of the compressor and fan motor create the characteristic droning hum that window AC units are notorious for.

Soundproofing materials applied around the appliance can dampen the noise emitted directly from the AC unit itself.

This allows you to comfortably run the air conditioner without the constant audible drone of the motor and compressor.

Allow You to Run the AC Without Disturbing Others

Even when properly maintained, most window AC units inherently produce noise in the 50-70 decibel range when running.

This is well above recommended background noise levels for comfortable living spaces.

The racket can make it difficult for others to sleep, hold conversations, concentrate on tasks, or simply relax with an AC unit humming away.

Adding soundproofing insulation around the unit helps contain the noise it generates.

This allows the window air conditioner to run while still maintaining noise levels that won’t disturb other members of a household.

Improve Sleep, Concentration, and Enjoyment of Your Space

Trying to fall asleep or focus while a loud window AC cycles on and off can be infuriating.

The machine’s incessant humming often becomes an intolerable nuisance noise that interferes with quality sleep and kills productivity.

Soundproofing removes this unwanted distraction, allowing you to comfortably enjoy activities in the room without the air conditioner providing an aggravating soundtrack.

Once treated with sound dampening materials, you can read, work, or relax with fewer distractions.

First Solution: Custom Window Insert

A custom window insert designed to soundproof a window-mounted AC unit. The insert, made of acrylic, fits the exact shape of the air conditioner, blocking exterior noise and dampening vibrations. Tubing with a dense rubber-like material seals the insert against the window frame and AC unit, creating an effective acoustic barrier. Considerations include the need for wide side panels on the AC unit and avoiding damage to ensure a gap-free custom fit for optimal noise blocking.

One method for effectively soundproofing a window-mounted AC unit is to install a custom sized insert that fits the exact shape of the air conditioner.

Here is an overview of the key steps involved with properly installing this type of noise blocking window insert:

Fits Shape of AC Unit to Block Noise

A replacement insert customized to match the specific dimensions of your window air conditioning unit will fill in any gaps around the appliance.

This prevents exterior noise like loud traffic from leaking in through small openings around a poorly fitted AC unit.

The insert also buffers noise emanating directly from the AC unit itself. This is accomplished by surrounding the window AC with a solid noise blocking barrier on all sides.

Made of Acrylic Which Insulates Better Than Glass

The window insert is typically constructed out of acrylic plastic rather than glass.

Acrylic is more effective at preventing sound waves from transmitting through it compared to traditional window glass panes.

The solid acrylic barrier works to reflect noise back rather than letting it freely pass through the open window area.

This significantly dampens both the interior noise coming directly from the AC unit as well as any exterior sounds trying to filter in through the perimeter.

Tubing Seals Insert Against Window and AC Unit

The window insert includes tubing made of a dense rubber-like material around its outer edges. This tubing serves to seal the insert securely against the window frame and air conditioning unit.

Compressing the tubing closes off any tiny air gaps around the insert’s perimeter, acting as an acoustic barrier to sounds trying to leak through.

The tubing also dampens vibrations and mechanical noise generated by the rumbling air conditioner itself.

This adds another layer of noise protection beyond the sound reflecting properties of the acrylic material.

Considerations for a Custom Window Insert

There are a few important considerations to keep in mind when exploring the option of using a custom sized window insert for soundproofing around an AC unit:

The window air conditioning unit should have side panels spanning at least 6 inches wide to accommodate a well-fitting insert.

Narrower AC units often cause issues with the tubing corners cracking or snapping off either during installation or continued use.

Cutting and trimming a standard window insert to fit the exact shape of the air conditioning unit increases chances of accidentally tearing the tubing.

Rips or gaps in the perimeter tubing can greatly degrade the noise isolation capabilities around potential air leaks.

If the tubing proves problematic, standard weather stripping could be used around the AC unit instead to simplify installation.

However, foam weather stripping may not create as robust of an acoustic seal compared to the dense compressed tubing.

Any dents, damage, or irregular dimensions on the AC unit itself will make it exponentially harder to achieve a gap-free custom fit needed for effective noise blocking.

Keeping the unit surfaces flat and blemish free provides the best surface for soundproofing.

Second Solution: Dual Window Inserts

A DIY project of building a soundproof box around a window air conditioner. The image shows the construction process, including precise measurements, cutting panels, and lining the box frame with mass-loaded vinyl for effective noise control. The final installation involves securing the box in the window opening, sealing gaps with acoustic caulk, and ensuring a snug fit for optimal

Another approach to soundproofing a window mounted air conditioning unit is to install a pair of window inserts placed above and below the appliance:

Create Two Inserts Without AC Unit

The first step is to create two separate window inserts designed to fit into the window frame on their own without the air conditioner unit installed.

These will be positioned one above the other once the AC is ready for use.

Remove Lower Insert to Install AC Unit

When the warm season arrives and it’s time to install the window AC unit, begin by temporarily removing the lower window insert. This opens up an empty space in the bottom portion of the window for fitting the air conditioner into place.

Fill Gaps with Insulation and Weather Stripping

With the window AC unit set into position in the newly opened lower portion of the window, inspect for any remaining gaps around the appliance.

Fill these spaces with flexible insulation cut to size. Adhesive weather stripping can also be used to seal up any cracks left between the AC unit and the upper window insert still in place above it.

Alternatives to the Dual Insert Method

There are couple variations on the dual insert soundproofing method that can be used as alternatives:

Rather than installing a solid mullion to hold the upper insert in position, L-brackets can be attached instead.

However, a fixed mullion is more effective for reducing noise transmission since it forms a continuous blocked gap.

The insulation placed around the AC unit can be decorated with paint, wallpaper or other finishes for a more attractive exterior appearance.

This improves aesthetics instead of just seeing plain insulation material from outside. Just take care to avoid any solvent-based coverings that could interact with the insulation itself.

Third Solution: Build a Soundproof Box

A step-by-step guide to building a soundproof box around a window air conditioner. The image illustrates the preparation of the AC unit, including turning it off, removing support panels, and cleaning the housing. The construction phase involves precise measurements, cutting panels from medium density fiberboard, and lining the interior with mass-loaded vinyl for effective noise control. The installation process includes securing the box in the window opening, sealing gaps with acoustic caulk, and positioning the AC unit within the box. Finish touches involve replacing window sills and caulking around the box perimeter for optimal noise reduction.

For DIYers willing to take on a more extensive project, a custom soundproofing box built around the AC unit provides superior noise control:

Prep the AC Unit

Before constructing the actual box, the window air conditioner itself needs to be prepped:

First, turn off and unplug the AC unit to safely handle it during the soundproofing process without risk of accidental operation or electric shock.

Detach and remove any existing window support panels, extensions or other fittings that are attached to the air conditioner housing. This provides flat, bare surfaces to work with.

Thoroughly clean the main AC unit housing, carefully removing any dirt, debris or dust buildup. Ensuring clean surfaces allows the sound dampening materials to properly adhere.

Build a Soundproof AC Box

With the window AC unit prepped for soundproofing, construction can begin on the noise blocking box:

Take precise measurements of the air conditioning unit and window area it will be installed in. Be sure to measure the full dimensions including depth, width and height.

Cut panels from medium density fiberboard, plywood or other solid materials to fabricate a box frame matching the measured dimensions. Leave a 1-2 inch clearance gap around the edges of the AC unit. This allows fitting the unit inside the box without scraping the sides.

Line the interior surfaces of the box frame with sheets of mass loaded vinyl. Mass loaded vinyl utilizes dense materials that effectively block sounds from transmitting through it.

Fill any remaining spaces in the box with additional sound dampening insulation or mats. This includes packing the clearance gap left around the AC unit itself to seal in noise.

Install the Soundproof Box

With the AC soundproofing box fully assembled, it can now be permanently installed:

Carefully lift the box frame into position within the window opening. Secure it by attaching screws through the sides of the box into the window framing or mullions.

Run a bead of acoustic sealant or caulk completely around the edges where the box meets the window opening. This seals up any small leaks or gaps where noise could potentially escape.

Slide the window AC unit into position within the box, engaging any rails or supports to hold it in place.

Finish Touches

Apply finishing touches to complete the noise blocking box installation:

Replace any window sills, trim pieces or moldings that were removed during the original window opening preparation.

Caulk thoroughly around the exterior perimeter of the box frame where it meets the exterior wall surface.

With everything sealed up, restore power and turn on the AC unit to perform testing. Listen for noise levels and make any final small adjustments needed to minimize sound down to a whisper quiet hum.


Employing one of these window AC soundproofing methods can significantly reduce noise problems during cooling season.

A custom acrylic insert, split upper/lower inserts, or DIY soundproof box all help contain bothersome air conditioner and outside noise.

This allows you to comfortably run the window AC unit with minimal annoying hums and distractions.

Contact a local insulation provider to explore your options and determine the best solution for soundproofing a window air conditioner in your specific home.

With a few simple modifications, you can achieve peaceful quiet cooling and finally sleep soundly through those dog days of summer.


Dominic is the chief editor of the Burton Acoustix blog which writes about acoustics and soundproofing to help readers with their queries and questions they might have with regard to improving any sound or noise issues that they faced in their life.