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.

[caption id="" align="aligncenter" width="480"] Noisy Air Conditioner[/caption] 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.

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