My portable air conditioner's compressor can get quite noisy, it's like a vibrating pulsing grinding noise. Is it possible to reduce this noise?

2 Answers 2


Check to make sure one of the (presumably plastic) panels that make up the exterior of the unit are not loose. My unit had a "fancy" black plastic border that fastened around the front panel, and it would over time begin to work loose as the compressor vibrated. I ended up wedging a little folded piece of paper between the front panel and the bordering plastic to get it to shut up.

Other than that, put something vibration-absorbing under it if possible, as Ed Beal suggests. There's not a lot to be done. These units are noisy because the usual outdoor bits are now in a box next to you. But if you need cool air, you need cool air!


There should not be any "grinding" but scroll compressors used in AC systems do have a large amount of vibtation they are normally mounted on 3 or 4 rubber vibration isolators for this reason. If you want to dampen a small window unit for example I have used 1/4" rubber sheet under the system to further isolate the noise, I would be cautious about the type of insulation as last year a friend had tried to put fiberglass around his new unit and although it worked he used two muck and the unit fell out and dammaged both the outlet it was plugged into and the condensing coil on the unit that was not repairable.

  • Yes the compressor in my unit does have rubber isolation feet. When I am able I want to try and see exactly what's making the vibrating rattling noise with the housing covers taken off. Can the noise be inside the compressor itself?
    – Kol12
    May 5, 2019 at 12:06
  • The compressor are noisy, I don't think they sound like grinding but they do buzz, other than that there are 2 fans usually driven off the same motor, if not set up correctly one of the fans (squirrel cages most of the time) may be rubbing.
    – Ed Beal
    May 5, 2019 at 15:24
  • The biggest contributor to noise can be resonance in the wall and window. Putting a reinforcing member under the air conditioner and putting vibration-damping foam (e.g. a foam-rubber kneeling pad) on the window might help. May 5, 2019 at 19:55
  • This is what I recomended, not the same wording, but not resonance, just simple vibration, having a degree in electronics and being a professional electrician I have only found resonant cavities 2 times over close to 40 years and both were light commercial facilities, the sonic vibrations was actually damaging the concrete in the first and creating huge standing wave interference in the second (a hospital) in both cases vibration from pumps was the cause. Simple addition of additional isolation in both cases fixed the problem.
    – Ed Beal
    May 5, 2019 at 22:47

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