Sound-proofing an air compressor?

I have two 500 liter air compressors that are quite noisy when in operation. They are enclosed in a big wire mesh box so I guess the best way to soundproof them would be by lining the wire mesh with some kind of material.

What can I use to block noise effectively? I will post some pics tomorrow to give you an idea of the size of the wire mesh enclosure.

Could you build a room around them and insulate it?

I was going to suggest building a stud wall around it (Drywall on bothsides) and insulate that, but I’d be worried about heat getting out.

First, make sure the compressors can still breathe…

Good old sheetrock/drywall/wallboard - about 3 layers. Most DIY big boxes sell 2’x2’ and/or 2’x4’ chunks, so you don’t need to schlep a full 4’x8’ sheet. Keep adding layers until the noise is acceptable

They may be depending on free convection through the wire screens to provide enough air flow to cool themselves. They may have pulleys with fan blades molded into the spokes, or some other means, and the motors may be TEFC (totally enclosed fan cooled) with an impeller and shroud at the end opposite the pulley, but these things rely on larger scale convection in the neighborhood of the machine to provide cooler air for the fans to exchange the hot air with. Putting something more restrictive on the screens could overheat them badly.

I have a small compressor that is pretty noisy, and I put a hose on its inlet (for another reason), and discovered that most of the noise went away.

This is the picture: http://img17.imageshack.us/img17/2903/img9386e.jpg. I guess that even if I cover the wire mesh completely with drywall or something, there’s still enough room in there for the compressors to not overheat. Also, only one of the compressors is in use. The other one is for redundancy.

Yeah, I’d think I’d build a stud wall around it, drywall both sides and put insulation inside it (or find some sort of sound deadening tile to put on the inside. Then you could either put a door on it for access, or you could probably just leave the left side of it open so any noise that doesn’t get absorbed goes up the stairs and (presumably) away from the work area.

There is a door actually. One part of the mesh is hinged and can be opened. And the stairs lead to the work area. This is the -1 level of an underground garage, the work area is on the ground floor.

I meant a door in the drywall/studwall. So you can get in and out.

I was thinking it would be easier to put the drywall or whatever directly on the mesh. Then I could still use the existing door with no modifications.

I suppose you could put holes in it and zip tie it, OR use drywall screws either screw it into 2x4’s that someone would hold on the other side or a piece of plywood. The problem is, that you’ll have all the noise bouncing around in that area against drywall and concrete, that doesn’t really seem like it’s going to absorb much sound.
If you want to go for cheap and easy like that I’d suggest getting some plushy throw rugs and lining the mesh and back wall with them.

This looks spacious enough that covering the mesh won’t cause them to overheat. If you think it’s worth checking, you could tape a plastic tarp in place for the sake of an experiment - much cheaper than doing it for real, in the event that there does seem to be overheating. But it’s not what I imagined when I worried about overheating.

You want mass per area to prevent sound from coming out of the enclosure. I think drywall is probably your best bet - cheap, heavy, and already part of any builder’s or maintenance person’s world. Heavy plywood would also work and would be more durable and more securely attachable to other things. Why not attach it to the existing screen? I like your idea.

Hanging plushy throw rugs will do some good, especially for hissing sounds and anything with lots of high frequency energy. If it’s more the deep sound associated with pistons and sucking air as each piston cycles, you need mass. You can always add rugs later.

Even if heat would be an issue, I think if he finds a suitable soundproofing design, all they would have to do is remove the top 4 or 5 inches and the bottom 4 or 5 inches and I think that would create suitable heat convection while not comprising the sound proofing by too much. But I’d be surprised if those compressors generated enough heat to cause a problem in such a big area, especially considering it’s below grade and I’d bet that concrete wall would act as a decent heat sink.

Part of the noise will be transmitted to the floor (particularlly thumbing bass) so mounting it on rubber mounts will cut some of that down.

If the compressors don’t have intercoolers, putting them in a closet will increase the temperature of the high pressure air by a whole bunch.
I know a guy that put his 10 horse compressor into a closet. When doing auto body work (sanders use a ton of air non-stop) the discharge air got so hot it melted the PVC pipe that he had used for air lines.
Lesson learned, you will need cooling air.

I guess the next question is “How often do they run?” If they only run for 3 or 4 minutes once an hour, I still don’t think I’d be concerned. OTOH if you’re running an auto body shop, maybe thinking about cutting a hole in whatever soundproofing material you’re using and mounting a box fan in it.

Something else to think of…It looks like there’s flourescent light mounted on the wall behind it, make sure it works, once you cover this cage, maintenance will be a bitch if you have to hold a flashlight while you’re working.