How to Quiet a Noisy Window Air Conditioner

Whether you have a window unit or built-in ducts, air conditioners are a necessity in warm climates. However, over time, they can develop a familiar rattle that doesn't seem to go away. Yet, turning the air off can be punishing. These irritating squeaks might seem like a small price to pay for the cooling benefit of an AC unit. Luckily, pros say that most noises don't require major intervention. Instead, check for minor gaps and routine maintenance to fix some of the most frequent causes of noise for air conditioning units.

1. Mind the Gap
A top contributor to squeaky AC sounds is gaps at the sides of a window unit. "Almost every manufacturer will provide a slider to fill the gap, which doesn't always do its job. Foam insulation on the sides is much better at silencing noise and helps keep cool air inside," says Mark Snell, owner and founder of Polestar Plumbing, Heating & Air Conditioning in Kansas.

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Rattling and clicking can also come from the vibration of a window unit against the window frame. If there's a gap between the base of the air conditioner and the window frame on the exterior of the home, you might need to mind that gap too. Support the weight of the unit by using mounting brackets, concrete slabs, or mounting rails. These securing mechanisms will help the air conditioner stay upright rather than tilt.

2. Insulate or Replace
"Ensure the seal around the window unit and window frame is in good condition and giving insulation. Good insulation will require the unit to run for shorter time periods to cool the space; holes and gaps will allow rushing air to add to the unwanted noise level," advises Steve Stewart, owner of Southern Comfort Mechanical in Texas.

Insulate the outer rim of the air conditioner with foam strips. If the problem persists, the culprit might be the window itself. If your windows haven't been replaced in decades, chances are that the panes are vibrating or the window frame might be splintering. If the insulation doesn't work, have a window expert come out to see if it will be cost-effective to replace the windows completely.

3. Get a Sound Blanket
Another option for quieting a noisy AC unit is a sound blanket. "You can also have your contractor install a sound blanket around your air conditioner compressor. A sound blanket is a great way to significantly reduce the noise level of your air conditioner without compromising its efficiency," says Snell.

If you live in a home with central air, your heating ventilation and air conditioning (HVAC) system includes a large compressor and condenser outside of the house. The hum can disturb people sleeping or working in adjacent rooms. An HVAC technician can install a sound blanket or air conditioner fence. You'll want a pro to do this so that the spacing is correct and the unit doesn't overheat. These blankets can also reduce the amount of dirt and dust that gets into the unit, and thus help prolong the life of the machine.

4. Keep It Clean
It's amazing how much dust and dirt can build up in air conditioning units. The particles can accumulate to make for a noisy—and allergen-filled—home. For central air units, have a qualified professional regularly come out to clean dust in the vents and in the compressor unit. Replace filters regularly and patch any leaks in the ductwork.

"Keep the filter screens clean by removing and washing them to allow the target airflow; same for the external coils. The gaps between the fins should be clear of dirt buildup. Follow the user manual on raising them, ensuring the unit is disconnected from power when rinsing," recommends Stewart.

For window units, the cleaning process can be completely DIY. The Department of Energy even suggests cleaning coil fins and condensation drains, as they can also affect how much energy the air conditioner requires to get the job done.