Silencing An Air Compressor - Woodworking Talk - Woodworkers Forum
 
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post #1 of 19 Old 08-10-2015, 05:12 PM Thread Starter
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Silencing An Air Compressor

I have a small Air Compressor which is VERY loud.

The goal is to reduce the noise from 94+ db to somewhere like 75- db.

Does anyone have any advise on how to reduce the noise or how to modify the compressor?

I have seen "box within a box" silencers that are supposed to work. Any one has any experience with them?

What about conversions using refrigerator or Air Condition pumps? Anyone ever tried it?
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post #2 of 19 Old 08-10-2015, 06:43 PM
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Put it outside.

Bob making sawdust in SW Louisiana
with a EX-21
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post #3 of 19 Old 08-10-2015, 07:19 PM
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you can enclose it

I have an oil less HF compressor that's very loud also. Mine's under the bench so that helps keeps some of the noise down. You would have to allow for some ventilation, but that can be worked out. Just locate the baffles in front of the vents and foam line the interior, keeping it away from any heat sources.

As far a refrigeration compressors they are completely different these days. My very first home built was from a refrigeration compressor, but that was 40 some years ago. It was from a 2 stage piston type and that worked OK, but I upgraded it as soon as I could afford it. My large 5 HP is also oil less and it makes a racket that you can hear from inside the house and the shop is 2 walls apart....

The answer to your question will only be as detailed and specific as the question is detailed and specific. Good questions also include a sketch or a photo that illustrates your issue. (:< D)
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post #4 of 19 Old 08-10-2015, 08:04 PM
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An insulated box might work, but I would be worried about heat buildup. You could put it outside. The best fix would be to buy an oiled compressor that is belt driven by an regular electric motor like on a table saw.
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post #5 of 19 Old 08-10-2015, 09:06 PM
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The best fix would be to shoot it and put it out or your misery.
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post #6 of 19 Old 08-10-2015, 09:15 PM
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Buy a better one, it's not going to be worth the effort.
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post #7 of 19 Old 08-10-2015, 11:11 PM
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I ran my compressor inlet out doors. That helped quite a bit.
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post #8 of 19 Old 08-11-2015, 06:33 AM
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You haven't given much info about the compressor?

Typical solutions are to box it in, or move it outside, both have considerations. Sometimes silenced intakes help as well.

I took at different route. My old Puma compressor pump died so I replaced it with a 2 stage Eaton pump. Not only does it produce a TON of air, it is extremely quiet. It's a slow RPM pump which contributes lower sound level.

This shows the difference in the pumps: The pump is rated at 72DB, and runs about 800-900 RPM.



It took a little effort to mount the pump and make a new belt guard, here is the almost finished product, with a home made cooler to help with moisture.


Last edited by Steve Neul; 08-11-2015 at 12:26 PM.
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post #9 of 19 Old 08-11-2015, 10:05 AM
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There are two factors contributing to the noise in cheap compressors, the oil-less pump and high RPM's. Many spec. listings tend to omit the decibel rating because it is so high so if you read oil-less or 3450 RPM stay away from it.

“Everything we hear is an opinion, not a fact. Everything we see is a perspective, not the truth.”
― Marcus Aurelius
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post #10 of 19 Old 08-11-2015, 10:49 AM
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For some reason I couldn't edit my post to add that my pump is rated at 72DB, and runs about 800-900 RPM.

You might have waited too long to edit. I fixed it for you.

Last edited by Steve Neul; 08-11-2015 at 12:28 PM.
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post #11 of 19 Old 08-11-2015, 12:59 PM
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I have had several Rol-air compressors in my business for 25+ years. Most have been Gas powered jobsite compressors or the small electric "trim" compressors. About 3 years ago my job site trailer got broken into and my almost new Honda engine gas compressor got stolen.
Among other items my insurance covered the loss. This time I didn't replace the gas but instead bought a twin tank Electric compressor. Wow, is that nice and quite. Even quieter than the small "trim" compressors. I bought that twin tank electric on a auction and paid only $100 for it. I am thinking of getting another that is right now on Craigslist.
Here is a link to the model: http://www.rolair.net/air-compressor...K17.html#specs

I am contemplating adding a storage tank to give me a more reserve of air so that the compressor doesn't have to start as much. Rol-air compressors are assembled in Wisconsin and are good quality machines.

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post #12 of 19 Old 08-11-2015, 12:59 PM Thread Starter
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Quote:
Originally Posted by tvman44 View Post
Put it outside.
If I put it outside I will annoy the c#@% out of the whole block!
I am not living in a little house on a priory. Even in small villages here the houses are very close to each other.

I can always wear internal and external earplugs and keep it inside, but my concern is annoying my neighbors.

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Originally Posted by Steve Neul View Post
The best fix would be to shoot it and put it out or your misery.
I do not own any firearms and even if I did, it would be illegal to shoot it anyway. Besides, I am only allowed to own smooth-bore shotguns where I live and the shot will ricochet and end up on my face so it is probably not a good idea.

The Compressor is relatively new; made in 2009 and I used it like 2-3 dozen times so most parts can be salvaged.

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You haven't given much info about the compressor?
Yes. Too bored to find the manual because modifying the compressor is actually "Plan B". If I decide that modifying it is the best course of action, I will go through the trouble of finding the manual.

Quote:
Originally Posted by woodnthings View Post
I have an oil less HF compressor that's very loud also. Mine's under the bench so that helps keeps some of the noise down. You would have to allow for some ventilation, but that can be worked out. Just locate the baffles in front of the vents and foam line the interior, keeping it away from any heat sources.

As far a refrigeration compressors they are completely different these days. My very first home built was from a refrigeration compressor, but that was 40 some years ago. It was from a 2 stage piston type and that worked OK, but I upgraded it as soon as I could afford it. My large 5 HP is also oil less and it makes a racket that you can hear from inside the house and the shop is 2 walls apart....
Yes, heat is an issue in the Summer, but usually the compressor will have to fill the tank a couple times; which make it already too hot.

What you describe seems to be vibration and/or low frequency noise. This is an issue for me because you cannot really do much about them.
It is like if your neighbors have a party and you cannot hear the music but you can "hear", or more precisely, feel the beat of the Sub-Woofer.

The house where I live happens to have an old American style A/C. The square thing that goes completely through the wall. The owners think about removing it so I can ask them if I can have it or even buy it from them if they remove it.

I may also be able to find a refrigerator that is 20-10 years old. Or maybe even 30, but 40, no, probably not.

By the way, I can most probably only get my hands on EU refrigerators. These comply with EU laws and guidelines and operate with 240V 50Hz power so they might be different than US refrigerators.

=====================================

I would not mind going with an option like making it Foot Powered via pedal. I do not use it for painting anything large or use it too often and it would also be a good opportunity for a workout.

But playing with things that can kill without knowing what I am doing is not logical, so I sit down and do "asking and researching".
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post #13 of 19 Old 08-12-2015, 03:48 AM
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About 40 years ago when I was in my 20's I couldn't afford a new compressor so I scrounged an old commercial refrigeration compressor which was wore out for its intended use. It was a 2 piston compressor as was probably equivalent to at least a 5hp maybe 10hp unit.

It worked good for a air compressor and would pump at least 150psi. It was real quite mainly because it ran real slow. The pulley on the compressor was about 18 inches. I used a 1 1/2 hp motor 3450 rpm and it had a V belt pulley that was as small as I could get, about 1 1/2 - 2 inches in dia. It went so slow you could almost count every time a piston would pump. It went slow but each stroke was a lot of volume. It had plenty of air to paint and most other uses. It wouldn't keep up with big air tools but that was fine, I'd just wait.

I did replace it last year with an new 5hp Quincy only because I started having troubles with the electric motor and other little problems. It also started leaking oil, after all it was probably 50-60 years old. I just got tired of messing with it.

Slow is good. Less heat and quiet.

Last edited by tewitt1949; 08-12-2015 at 03:52 AM.
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post #14 of 19 Old 08-12-2015, 09:26 PM Thread Starter
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This is a very nice story tewitt1949!
I would love to see pictures of your build!


I really do not know what to do with the compressor yet. I saw some YouTube videos that use computer fans for case ventilation and it makes sense.


Here are the videos that I watched:

https://www.youtube.com/watch?v=UOpB6oD2lt4

https://www.youtube.com/watch?v=C2zIP6TtQw4
(My compressor is also Einhel made and of similar size to this one)

https://www.youtube.com/watch?v=Txs5Q2V85P8


A box is something that I can do anytime. I know how to rig computer fans and all the wooden parts I can "order" from local furniture makers (meaning that I will ask them to keep any scraps and cut my pieces out of them). No table saw in my shop...

Anything else is just too permanent.

Besides, I do not have any refrigerator parts at the moment and I cannot know when I will find them unless I sabotage the refrigerator of someone I know of course!

I most probably can make the compressor leg operated via pedals but it seems that not many have done that.

Buying a new compressor at the current moment is out of the question.
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post #15 of 19 Old 08-13-2015, 08:12 AM
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Putting the compressor in a box would burn it up. It needs to cool itself as it runs. About the only reasonable thing you could do is install it somewhere outside the shop. They do well outside out of the dust. You just need to put some kind of awning over it.
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post #16 of 19 Old 08-13-2015, 04:19 PM
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If you want to drop the decibel level by a good 30-50%, build a box with no bottom and staple some old carpet to the inside. Slide it up against the wall with the compressor under it and see how hot it gets after a couple empty-to-full runs. We used this method with a 200 gallon compressor in the machine shop I worked at as a teenager, they just cut a few small holes at the top and bottom to let it breathe. It was still definitely annoying to talk over, but no earplugs were needed working right next to it.
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post #17 of 19 Old 08-13-2015, 05:58 PM
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Quote:
Originally Posted by Steve Neul View Post
Putting the compressor in a box would burn it up. It needs to cool itself as it runs. About the only reasonable thing you could do is install it somewhere outside the shop. They do well outside out of the dust. You just need to put some kind of awning over it.
You could build a 4 sided wood box, leaving the back open. This will buffer the noise, but allow the unit air. If you insulated this box on the inside with sound-deadening, you might reach the 75db you're wanting. The insulation can be as cheap as old egg cartons or batt insulation or whatever else you think will dampen sound when stapled inside the 4 sides. Since the box will have a top, it becomes a table or work stand.
Think of putting a radio in a box and turning it around backwards to face the wall. Hey, where did the volume go?
Something to try.
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post #18 of 19 Old 08-13-2015, 06:25 PM
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Quote:
Originally Posted by Toolman50 View Post
You could build a 4 sided wood box, leaving the back open. This will buffer the noise, but allow the unit air. If you insulated this box on the inside with sound-deadening, you might reach the 75db you're wanting. The insulation can be as cheap as old egg cartons or batt insulation or whatever else you think will dampen sound when stapled inside the 4 sides. Since the box will have a top, it becomes a table or work stand.
Think of putting a radio in a box and turning it around backwards to face the wall. Hey, where did the volume go?
Something to try.
The experience I have with compressors is they need a lot of air circulating over them. When ran a lot they generate a lot of heat. I've even set up fans blowing on the compressor under heavy use to prevent it from burning up. I sure wouldn't put even a three sided box over it unless you had some means of blowing cool air on it too.
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post #19 of 19 Old 08-13-2015, 06:30 PM
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Quote:
Originally Posted by Steve Neul View Post
Putting the compressor in a box would burn it up. It needs to cool itself as it runs.
I can vouch for this. I recently put my small pancake compressor in a wooden cabinet with several 1 1/2" holes in the back and it gets way too hot in there without the door open. I just ordered a cabinet fan to see if that will do the trick.
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