Noisy A/C Help

Hi Ted,

We found your informative blog while doing a Google search for idea to solve our problem and we were wondering if you might be able to help us with some suggestions? We’re at a loss for what to do. The problem is, recently, our neighbors, who themselves, do not have any A/C or window units, keep their old windows (i.e. they are not storm windows so do not have much sound insulation) open during the hot Boston summers. My husband and I live in a 2-family house. Our larger unit has 2 A/C units and the people in the 1st unit have one (please refer to attached pictures). According to our neighbors, whose bedroom window on the 2nd floor immediately faces all 3 A/C units, make a lot of noise which is bothersome at night when they are trying to sleep.

I tried to attach some pictures so that you might be able to get an idea of our situation but they wouldn’t go through to your email. We’d greatly appreciate any suggestions! And of course, we’re looking to be cost effective.

Many thanks for reading this email! We hope to hear from you at your earliest convenience.

Jeanne & Paul

This is going to be a tough one. I say this because of the space that we don’t have (in this case) around the AC units. I will do my best to explain how I see the situation, but please feel free to contact me or shoot me a reply E-mail. By the way, thank you for the pictures, they are an incredible help!! By the way, sweet Porsche. : )

I quickly did some photo-shopping to your picture, see the attached image. Even though it is a crude representation, the blue lines show the path of the sound. In this case, you not only have the sound that is going directly from the AC unit to your neighbors window, but you also have the sound coming out of the top and the back of the unit, bouncing off of the house and making its way to their window. This is such a narrow space with all hard and parallel surfaces, the sound just keeps bouncing from house to house and has no where to be absorbed. So, if you think about it, the sound that your neighbor hears could possibly be as if you had 2 or 3 times the amount of equipment out there running because they are hearing the direct noise as well as noise from two or three different reflection points.

Fixing the situation, like I said, is going to require some creative thinking. I am not an HVAC contractor, so you will likely need some outside consultation on this one, but I do know that these condenser units need a certain amount of room around them to function properly. You don’t want to put something too close and have it destroy the machine, so make sure to find out what that distance is for all three units so they can breathe.

In order to reduce the noise that your neighbor is hearing you are gong to need to do two things. First would be to interrupt the line of sight path of sound transmission. This is going to mean building a “wall” or a structure high enough so that they can not look out their window and see the units. Due to the angle and the distance here, that might be hard to do. Furthermore, the wall is going to be a certain distance from the units, which I am guessing would be past the side walk, and out in the grass, making the sidewalk INSIDE of the wall would work, I guess, if the wall near the gutter in the picture was not there? The second thing would be to take away the reflective surface behind the units by covering up the siding with some kind of absorptive blanket so that the sound is not going to be able to bounce off of the house and over the wall.

I will attach a few pictures of an installation that I did for a customer earlier this summer. In his case, the fence was already there, and he had a LOT more room to work with, but it will give you an idea of what I am trying to illustrate. Ideally, the height of the wall that you want to build is two-times the height of the noise source, but in this case, due to the height of the window.

I would suggest one of the three following products. The first two are going to perform better than the last one as well as last a lot longer outside, but they will both help. They will all need some kind of a structure to which they are to be attached, but the structure options will vary depending on which product(s) you think will be the best for the situation.

Exterior Grade Barrier Backed Curtain: EXT-BBC-T14-2
These are custom made which effects the price, but they are usually around $13.00-$14.00 per square foot

EXT-QFA-7 as an absorptive panel on the house, Exterior Quilted Fiberglass Absorber
These are also custom made which affects the price, but they are usually around $6.50-$8.00 per square foot.

I don’t have a dedicated web page for this yet, but should have one shortly. It’s basically ONLY the quilted facing for the EXT-BBC panel above. It’s a “blanket” of 2″ thick fiberglass with a scrim backing and an exterior grade vinyl facing and edge binding.

Sound Silencer acoustical wall panel.
1″ or 2″, and I would only recommend Charcoal as the white breaks down extremely quickly with ultra violet exposure. Panels: 2′ x 4′.
1″ Thickness: $5.50 per square foot
2″ Thickness: $7.50 per square foot


  1. sugiat

    Hallo Ted,
    I want to reduce noise that come from condensor chiller machine, right now sound intensity is over than 90 dB but it should be reduced 20 dB down. My question is what kind of suitable material for sound proofing should I put on my panel wall. Need your answer soon.
    Thanks for your kindly respond.
    Best Regards,
    Bandung – Indonesia

  2. Ted W


    Thank you for the question. If you can get me some additional information about the situation, it will give me a better position from which to make suggestions as to how to proceed. Either some sound pressure data which would tell me what kind of frequencies you are dealing with would be REALLY great. There are even iPhone or Droid apps you can download for free that will give you some data. It may not be the best but it’s something. Even your description of the sound “a low humming noise” or something would be good. Also, if you could E-mail digital pictures of the space to me, that would be really great.

    Without that information, I would suggest the exterior grade quilted blankets be installed between you and the noise source. These would ideally be spaced off of a building by even a few inches and eliminate the line of sight from your listening position to the noise source.


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