All air conditioning units will generate some type of sound. The noise can be categorized as either structural or airborne. Let’s go through the different types of noise you may be hearing, and what sounds may require professional attention.

Structural Noise

Structural noise is sound energy that travels through solid material, which you would feel as vibrations. In this case we’re talking about vibrations transmitted from the air conditioner into your home. This is most often a problem with wall air conditioners, air conditioners placed on the roof, or units that are on a wood platform and attached to the house. To reduce structural noise you need to decouple the air conditioning unit from the material it’s vibrating against, so that the hard surfaces don’t come into contact with each other.

Airborne noise

Unlike structural noise which is transmitted through a solid object, airborne noise is sound that travels through the air. This is a concern with any AC unit, and mostly due to how loud the parts of the A/C unit are, like the fan or compressor. To stop this noise, create a barrier to block the path of the sound and install sound dampening foam to keep noise from reflecting off surfaces (like walls) surrounding the unit.

Alright, so there are a lot of types of noises an AC unit can make. If your unit is operating normally, the next step is treating the structural or airborne noise that you want to reduce. Let’s walk you through a few strategies from isolating the unit to building a physical barrier. You may need to use a combination of these approaches, as many units generate both structural and airborne noise. Here are your different steps you can take to soundproofing an air conditioning unit:

StEP ONE: DECOUPLE THE AC UNIT FROM THE FLOOR AND BUILDING

This problem is most often experienced with air conditioner units that are on the roof or attached to a wall. You need to decouple the air conditioner from your home’s structure. The ideal method here would be to use 100% rubber vibration isolation pads (like our Super W pads) or an isolation mount designed for heavy machinery. You can also utilize a 100% rubber mat, but make sure it’s rubber!

A common mistake is to use vinyl or bricks, these are not effective! You need 100% rubber to decouple the unit and prevent vibrations from transmitting into the surrounding structure. It’s important to pick products with the correct deflection rate based on the weight of your AC unit. Start by checking your manufacturer’s specs to determine the weight of your HVAC unit. The pads we use perform best with 1 pad per 40 pounds of machinery. If your unit weighs 160 pounds, you should use 1 pad per corner. If you have an industrial unit and need neoprene sound isolation mounts, be sure that the weight load for the mount matches up with the weight of your unit.

Once you’ve decoupled the unit from the floor, tackle any wall space the unit is up against. Noise can move through anything connected to the unit, and it can get quite loud, so you may need to soundproof ductwork to handle that problem. Do your best to get your unit off of whatever it’s touching. We suggest creating a small gap and filling it with acoustic sealant. You can also use the same rubber isolation pads we talked about earlier at any of the connection points to accomplish the same thing. Note that some parts of the unit won’t be able to be decoupled, but if you’re treating all the other areas you’re doing the best you can do.

The above solutions are recommended for an average residential unit. If you are looking to treat a commercial unit, give us a call and we can offer solutions using neoprene isolation mounts.

Air Conditioner Noise Reduction for Airborne Noise

The best way to stop a noisy air conditioner is to build a soundproof enclosure or fence aorund the unit, and add both sound absorbing and sound block material to the walls of the enclosure. Make sure to leave room for ventilation!

Here are a few keys to building an effective soundproof fence, noise barrier, or soundproof shed:

1. Build it close to the noise source, in this case the air conditioner unit. The closer the barrier is to the noise source, the more sound it will be able to block. Be sure to leave enough space for ventilation.
2. Build it high. sound radiates outward through the air, so to block it effectively, extend your barrier 1.5 to 2 times the height of the unit. Two times the height is recommended.
3. Extend the barrier either around your unit or well past it to stop the sound from flanking the sides of your fence. Rule of thumb is to extend the wall 4 times as far as it is close to the unit. For example if the wall is 1 foot from your unit, it should extend 4 feet past it.
4. Create an airtight barrier. Sound moves like water and can get through the smallest holes. You shouldn’t have any gaps in your barrier.
5. Use a dense material. Dense materials are great at sound blocking, which is why we recommend using an MLV sound barrier or BlocknZorbe. Additionally, while wood is good, bricks or concrete will be even better.
6. Add absorptive material. Wood and metal will reflect sound, so by adding absorptive material like BlocknZorbe or our Quiet Quilt Outdoor Acoustic Blanket on top of your fence, you can better block and absorb the noise. If you have a chain link fence, you’ll absolutely have to use the Quiet Quilt Outdoor Soundproof Blanket which includes a noise barrier.

For the most effective barrier, we recommend not just building a fence, but creating an enclosure all around your unit, similar to build a soundproof pool pump box or fence. You can cover 3 sides, but for optimum performance, cover all 4 sides. Follow all the same rules above and be sure to create barrier walls that are tall, airtight, and covered inside with absorptive materials. For the top, build a slanted roof with an opening facing away from your home, this will allow ventilation for your unit, and direct the noise away from your house.

Remember, don’t fully enclose your HVAC unit! Although we want to do what we can to soundproof your air conditioner unit, we don’t want your unit to break entirely. Cutting off the ventilation or wrapping the unit to cause it over to overheat is a great way to break it. I guess then you can buy a new quieter one…

Soundproofing Your Home from noisy AC Unit

Soundproofing immediately around the air conditioning unit is the most cost-effective way to reduce noise, but in some situations you'll need to consider soundproofing the house itself. The most common path for noise from an air conditioner positioned outside a bedroom to get into the home is through the window. There's multiple ways to soundproof a window, as well as varying costs of soundproofing a window. When it comes to soundproofing a wall, the window is typically the weakest point due to its lower STC rating.

By adding Fantastic Frame window inserts to an existing window, you will reduce the noise through the window by up to 80%. Depending on your configuration, the window may not be the weak point and so you'd need to look into how to soundproof a room. If you're unsure on what to do, you can always reach out to us and we'll talk through solutions with you. If your furnace or HVAC unit is in a closet, check out our how-to article for a soundproof hvac closet.

Banging or Clanking - There is likely a loose, out-of-balance or broken part. Your compressor may need a replacement, or the blower or fan could be hitting other parts inside your unit.

Clicking - Clicking upon start-up or shutdown is normal, but if the noise is constant your control may be defective, or the thermostat might be failing.

Buzzing - There’s a host of reasons your AC could be buzzing. Loose or out-of-balance parts, debris in the unit, parts or lines rubbing together, or even a dirty condenser coil or air filter. If you notice that your unit is running, but your home isn’t getting cool, there is likely a refrigerant leak.

Squeaks & Squeals - For some units, this noise may be normal on start-up. If you’re hearing it consistently it’s likely that a part is going bad. Fan & blower motors, as well as the blower wheel and housing will squeal when they malfunction.

Humming - Humming may not be serious but still shouldn’t be ignored. This could be electrical issues or vibrations from loose parts or refrigerant piping. If you hear the compressor humming but not starting, there may be an issue with the motor.

Rattling - This may be as simple as debris in your system, but if not, it may mean your unit is starting to deteriorate. It’s likely parts are loosening. Check for loose screws or bolts and clean your condenser coils and air filter.

Screaming - DO NOT IGNORE THIS NOISE. Immediately shut your air conditioner off and call a professional. You’re likely experiencing a refrigerant leak which can be dangerous to the health of anyone in your home. It may also indicate a pressure build-up within the compressor, which is also dangerous.

Pulsating - A pulsing noise can be normal, but if it’s so loud you’re hearing it inside, it may mean something is loose. Often the culprit is the fan motor or blades.

Whirring - A helicopter-like whirring noise is often due to a broken belt, bad bearings or a faulty fan in the blower or outdoor unit. As the fan starts to get loose, it can result in a whirring noise. Sometimes it can just be the sound of paper or debris stuck in the fan somewhere.