Tip: Reducing compressor noise.

chinch · #1 04-07-2010, 03:43 AM

My 3.5 hp oiled compressor is noisy when running to the point where a conversation cannot be held while it is running. So this weekend, I built a compressor box which I thought might be of some interest to others.

The box is made of 18mm MDF, and measures 1.2 x 0.8 x 0.6m. It is bottomless to fit over the compressor, and the double thickness lid is removable.

The air feed is taken out through the side (front?) wall into a water condenser and teed to a quick connect for painting. From there it goes through an oiler to two regulated quick connects - one set to ~80 psi for drilling, and the other set to ~30 psi for rivetting.

With the lid removed, you can see the compressor inside the box. The box has a single thickness wall, with an "E" shaped baffle at each end to allow air to flow through the box without letting too much sound out. The inside of the box is lined with rubber carpet underlay, and a power strip is mounted inside the box to deliver power to the compressor and a 12v power supply for the extractor fan on the outlet side.

With the lid propped up, you can see the double thickness lid, which fits very snugly inside the top - a quality fit is essential here to keep the noise inside the box.

The aluminum vent covers the baffle inlet, which is routed upwards through a series of MDF baffles to enter the box via a 120mm hole on the inside. The other end is identical but has an 80 cfm fan to assist in the movement of air through the box. You can also see that the compressor and the box are sitting on double thickness of underlay, which is used to prevent compressor vibration being transmitted via the concrete floor to the box.

Well, I was surprised just well it worked. When the compressor is running, it is now only slightly louder than a chest freezer. Noise levels are vastly improved over the compressor alone.

How am I going to improve it? My next job is to put an access hole in the front so that I can easily check the oil level and drain the tank regularly - "out of sight, out of mind" is definitely a bad idea in this instance. I will also connect a temperature probe inside the box to a display readout outside and use it to trigger the extractor fan when the temperature gets too high. Only then I will be happy that I am not going to destroy my compressor through overheating. I am also going to make the lid pull double duty for tool storage by fitting a piece of foam to the top and cutting out holes for airtools, bucking bars etc.

This mod has made my workshop a much more pleasant place to be.

JAT · #2 04-07-2010, 04:44 AM

Chris,

Great job on the compressor silencer box! My compressor is a Sears oil-less variety and you can't scream loud enough for a conversation while it is running. I am about to start riveting again and dreaded the noise, so the timing of your thread is perfect. I am off to Home Depot for some material. Thanks for the inspiration!

Jim

170 driver · #3 04-07-2010, 05:41 AM

Heat may be a factor, the compressor gets pretty hot with alot of use. May need to add a fan and some vents.

Jamie · #4 04-07-2010, 08:02 AM

I built something similar (although not quite as nice). It was ventilated but it did burn up two compressors. I would use caution.

Mike S · #5 04-07-2010, 10:10 AM

Gotta agree with the advice about heat-------I would look at ducting the outflow side of the units cooling fan out to the exterior of the shop, and provide adequate inflow air for make up.

Also, the pressure regulators ganged together, ????? If you have trouble keeping the low side accurate, try splitting the feed with a "T" so each one sees tank pressure.

The drain can be run outside of the box, valve where it can be easily reached. Right now it looks like you might need an extra elbow in your arm to reach the drain.

Otherwise great job. I really like the idea of storing the tools on the lid in designated cutouts.

aerhed · #6 04-07-2010, 10:25 AM

Kinda off topic as usual, but someone told me about a guy who uses windmills to pump air into storage tanks (a bunch of em), and he uses this as an air and multiple alternative energy source (pneumatic electric generation). I'll bet that's a quiet air source, if you don't mind air tanks everywhere. The compressor noise has driven me to as many electric tools as possible. I keep looking for an electric rivet gun. Any ideas?