A/C Compressor Noise

A.C Compressor Noise

We recently purchased our home and to our surprise, the outdoor A/C compressors are extremely noisy. Normally, this would not be an issue, however, they are located right out side our master bedroom windows.

I feel that our problem is two fold.

  1. The compressors are noisy
  2. There is an intense amount of vibration from the stand

The units are sitting on a 4′ x 8′ stand roughly 7′ off the ground. The units have to be above ground due to our home being in a flood zone.

I read quite a few posts you made about building a perimeter around the units and using the sound deadening vinyl pads to silence the noise. I completely agree with the strategy but am wondering what your thoughts would be about silencing the noise coming from the vibration of the units themselves, if any.

I have attached a few pictures of the affected area. The windows directly above the units are for our bedroom. I have also included a shot of the nearby oak tree which also reflects sound towards our home.

I would love to purchase your products and can’t wait to hear back.

Noisy Air Conditioner

Noisy Air Conditioner

OK, right into the situation – the pictures are a huge help, thank you for that!  Based on your description of the problem, I would probably taking this in a two or three step process to make sure that you take the right steps while spending the least amount of money. The thing that worries me the most about this situation is the vibration introduced into the stand and the house. If I were you, I would probably start by calling a few local HVAC contractors to get bids on coming out to see if these machines are balanced – if this is even applicable. Vibration energy is a MUCH greater problem than airborne noise because it is a much more violent type of energy. Example: Take a coffee cup and put it onto your desk.  Pound the desk with your hand and notice the rings in the coffee. Now yell at the cup as loud as you can (but not into the top of the cup) and see how many rings you get.

You should first eliminate (or try to eliminate) the structure born vibration that is being introduced by the machines running. This can be done in a few different ways – and the best is going to need to be determined by you and possibly with the help of a local HVAC Contractor. IDEALLY, I would like to see some kind of spring isolator between the compressors and the stand. There are a LOT of different types of spring isolators and choosing one is going to be dictated by the environment, but you may want to look at the SLFH un-housed spring mounts or the C, CIP or CIW Housed spring mounts. The SLFH are cheaper but because they are un-housed, they could potentially blow over. You may be able to get around this by coming up with some kind of strapping or something, but that would be up to you. If you don’t have the room for this, you may get some reduction out of the Super W pads which are simple neoprene rubber isolators that will only need ¾” of height.

If you can lift the units up to accommodate for the springs and a new layer of ¾”, exterior or marine grade plywood, I would use the springs in the four corners and make a “floating table top” on top of the frame that is there now. That will let you use four springs which will limit the points of contact the machines have with the frame and be cheaper than buying eight of them.

Personally, I would start here and see what this does. It MAY reduce it to an acceptable degree in which case you can move on to your next project. If it doesn’t reduce it to a point where you are comfortable, I can make additional suggestions but those are going to depend on the relative reduction offered by the first step.

If they are simply making a TON of airborne noise (which I kind of assume they are) I would assume a large amount of that noise is coming in through the windows. If you consider the wall as one entity, the windows are the area of the wall that have the least amount of mass and density, so that is naturally the path of least resistance that the sound is using to make it’s way into the house.  Assuming this is the case, I would strongly suggest the Climate Seal Acoustical Series window inserts. These are ¼” thick panels of a clear acrylic that have a magnetic bellows system around the perimeter of the window (like the bellows of the seal on your refrigerator door) that snaps into place with magnets. You will, of course, need to install a thin metal “L” angle around the window so that the magnets have something metal to snap onto, but this is very simple. I can explain this further if you would like but it basically adds a dead air space between your existing window and a new “window” and will significantly reduce the amount of sound making it’s way into your bedroom.

I hope I have not confused or overwhelmed you. Please let me know what you think of all this.


16 Comments

  1. Richard Agins

    My neighbor has a very noisy comperssor and is unwilling to build an enclousure to reduce the sound. What about noise reduction blankets? Do they work?

  2. Ted W

    Richard,
    The exterior grade sound blankets work extremely well but they do need a structure to support them as they are not a free standing product.

    -Ted

  3. Jeffrey Masnari

    I have a Trane 13i compressor which with the top off makes little to no noise other than the fan and motor. Truly a very quiet unit. Unfortunately when the top is placed on the unit,, both in a unsecured manner and a screwed down manner, the unit starts making vibration noises. I eliminated the worst of the noises by removing Trane’s plastic name plate that snaps into the front of the compressor, wonderful design idea that was. I have also placed rubber washers top and bottom of the screw holes that attach the top and that makes for a more uniform somewhat better humming vibration sound. But, being obsessive and living in an area where my closest neighbors don’t have AC I would like to acheive the lowest possible decibel level for the unit. Other than leaving the top off, which I assume would invite all kinds of trouble, is there any other suggestions you might have to reduce the compressor noises I have described? I was thinking about better isolating washers for the top to body connection but thought I’d check with somebody who might have some better idea’s.

  4. Steve

    I’m having trouble with this as well, we have Quietside units which the builder put in about 6 feet from put neighbors bedroom / office window. we’d love to accommodate her, but moving the units is impractical on many counts. I’d love to send you some pictures – whee can I send them to?

  5. Robert Solomon

    noise from house next door compressiors. The house next door has two compressiors mounted
    about 8-10ft up above the ground.Which is about 10ft from our property line which gives us alot of noise on our deck.Which is also up about ten feet.We were thinking about enclosing the deck with a wall on the one side to buffer some of the sound with planting bamboo trees would work? If you can suggest any other means to lower the nosie level I would appreciate your knowledge.

    • Ted W

      Hey Robert, thanks for the comment.

      Trees are NOT effective noise barriers. They can be relatively good visual barriers, but they are not going to block a measurable amount of sound. You will need some kind of exterior-rated sound wall that will introduce a decent amount of mass between you and the noise source. The wall will need to be as air-tight as possible as sound travels through air. Thus, if you have air space connecting a noise source with a listener, the sound can get from one to the other relatively easily.

      A panel such as our Exterior Grade Quilted Blanket would likely be the lowest cost method of blocking the sound to a relative degree.

      Please let me know if you have any more questions. Thanks, Ted.

  6. Tom Noone

    I have a summer home on a channel connecting to a beautiful lake. Our group of 27 homeowners installed an aeration system in the water. The channel is roughly 1200 feet long by 200 feet at its widest. Near the center 120 feet back from the waters edge is the compressor system which consists of two compressors feeding air through a manifold to five buried airlines connected to ceramic diffusers spaced about 200 feet apart in the center of the waterway. We have a neighbor adjacent to the compressor that objects to the sound. We have put up a fence between this homeowner and the compressors as well as had a sound enclosure fabricated from fiberglass covered with an asphalt like coating – this has vents in it. This was the suggestion of the installation contractor. We have had several attempts at further suppressing the noise using insulating foam sheets strategically placed around and over the current noise cover. We have had an engineer come out and test the noise level and while we are not breaking any noise ordinances we are as noisy as an ac compressor which runs constantly. Any suggestions on a potential solution or remedy would be greatly appreciated!

    • Ted W

      Tom,

      Thanks for the comment. Is there any chance you would have time to take a few pictures and send them my way? A visual representation of the situation would give me a much better position to do my best to make some recommendations on how to fix this for you.

      The product that I have had the largest success with over the years is the Reinforced Exterior Grade Sound Blankets. These are essentially custom-made blankets where we quilt a nominally 2″ thick fiberglass (absorber) layer to a 1lb per square foot Mass Loaded Vinyl (sound barrier). These blankets are made with grommets to be used as points of attachment as well as vertical Velcro seams to attach one panel to the one next to it. Because they are made on a per-job basis, I would need an idea of the dimensions in order to determine a cost.

      I look forward to hearing back from you. Thanks,
      Ted

  7. LDR

    Imagine a new rustic home in a wooded area and a fairly large ravine (roughly 150′) out back with a pond at the base of the ravine. It’s a very serene, picturesque setting, a pond with a walk around path, and a pier extending a good distance out over the water. All this is carefully groomed into place and lending itself well to the sound of a Scroll compressor invading the calm.

    The refrigerant charge is verified and equipment manufacture’s usual sound blankets are installed. There’s nothing wrong with the equipment; it’s just the typical sound characteristics of the higher efficient Scroll compressors that we are trying to dampen.

    • Ted W

      Do you happen to have any pictures of the equipment that you could send? Any specs on the manufacturer’s sound blankets?

      With that information, I’ll do my best to help! This sounds like an AWESOME place to be (without the noise, of course!)

      Thanks,
      Ted

  8. Alex

    Hello,
    I have two heatpump units on the wall of the house under my two windows of master bedroom on second floor
    I was planning to build some kind of envelop with the sound blankets around these units and above ( as the major idea is to stop noise going up to the windows of the bedroom)
    Please suggest what is the best way to do it
    Thanks

    • Kyle Berg

      Hi Alex,

      Thank you for the post!

      There are a couple of potential noises that are occurring here. The first would be airborne noise, and the second would be structural vibrations. These can both be stopped in your scenario. The one problem with building some form of enclosure for this unit, would be that these typically require ventilation. To build an enclosure over these would not be ideal because of this.

      What I would suggest to stop the transfer of airborne noise, would be our Climate Seal Window Inserts. These are ¼″ acrylic inserts that are installed on the inside of the home, in the frame of the window. These are magnetically attached to a trim that is installed in the window jamb, so that you can easily remove the inserts when you would like access to the window. This adds mass and density to the window area, as well as creates an airspace between the window and insert, which allows noise to dissipate between the two surfaces. This form has the instructions on how to measure your windows properly, to ensure a tight, accurate fit.

      The structural vibrations, if these are occurring, can be stopped by isolating the unit from the structure. When the motor is spinning, this can cause the unit to vibrate, which then transfers this vibration to transfer to anything that it is touching. There are quite a few different styles of isolation mounts that can be installed under the feet/mounting points, to stop this transfer of vibration from the unit itself. In order to find the right ones, you will need to find out the weight of the unit, then number of mounting points/feet it has, and how big these are.

      Please feel free to let me know if you have any other questions on this.

      Cheers!
      -Kyle

  9. Keith

    Hi there.
    I just bought a beautiful Townhome which is 3 levels. My neighbors terrace is attached to my 3 level and this is where he has 2 Ac compressors which seem to run 24/7. They are both on stands and are about 1-1/2 feet from my wall. My issue is im hearing a humming noise whenever their Ac is on which never goes off! I live in florida so bad news there.
    How can I soundproof the vibration or humming noise which I can hear all the way to my first floor?

    • Kyle Berg

      Hi Keith,

      Thanks for the post!

      What is happening with these A/C units, and why you are hearing this humming noise/vibration, is because it is creating a structural vibration on the terrace. This can be stopped, though!

      The units need to be isolated from the terrace and the walls of the townhome. You can do this by installing isolation mounts on the feet of the units. Depending on how severe the vibrations are, you may need to isolate the lines that are running into the home as well. You can do this by making the holes leading into the home slightly bigger than the diameter of the lines, then use Acoustical Sealant to fill in that void. This will stop the vibrations from transferring off of these lines, onto the structure of the home, which is transferring across the surface of the home.

      In order to find the right isolation mounts for these A/C units, you would need to find the weight of the units (should be in the owner’s manual, or you can contact the manufacturer) and will also need to find out how many feet the unit is standing on.

      Feel free to let me know if you have any further questions.

      Cheers!
      -Kyle

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