Noise Insulation/Suppression

[ChrisHParticipant @chrish]

I have a little air compressor in my workshop which is very good but very noisy, not only for me working in the shop but for the neighbours too.

I need to box it in using some form of sound deadening, whilst still allowing it to suck air. Boxing it in is not the problem; insulating the sound without spending a fortune is.

Any ideas on what to use for noise insulation that is cheap? The box would only be about 2ft x 2ft x 1ft – it is only a little compressor!

[ChrisHParticipant @chrish]

[John Stevenson 1Participant @johnstevenson1]

Probably a direct drive one ?

These are very noisy, I had one, still have it actually but it's not wired in, and it was terrible. I have it in the hay loft but can't run it without feeling really guilty .

Finished up getting a better compressor and plumbing both tanks together for volume. I bought a hydrovane but don't think they do real small ones, also have one of these Bambi compressors just for the odd bit of blowing off and these are that quite I keep forgetting to switch the thing off.

[martin perman 1Participant @martinperman1]

I and my brother have recently had to line the inter connecting wall between my mums house and her neighbours so he cant hear her telly, at the age of ninety she will not accept she is deaf, any way we lined the wall with noise absorbtion tiles, soft foam with plenty of voids, which were approx 12 inch square by 40mm thick, her neighbour reports he can no longer hear the telly even though mother still has the volume up high, our sister found the tiles on the internet.**LINK** £37 for24

 

Martin P

Edited By martin perman on 26/01/2014 16:49:52

[Gone AwayParticipant @goneaway]

For airborne noise, ideally a closed box. Perhaps lined with an acoustic absorber …. depends on what you make box from (cement blocks for instance might do it alone but you may not want that). As soon as you make a hole in the box, though, an awful lot of the sound is going to come out. It can help to make a labyrinth passageway of the hole.

For structure borne noise you'll need some kind of shock-absorbing mounts.

How come it's so noisy? My compressor is in the garage with no noise/vibration precautions; my workshop in the basement diagonally adjacent and I can't hear it from there (no machines running). I can barely hear it from outside the garage with the garage door closed.

[RJWParticipant @rjw]

I can sympathise and probably not what you want to hear, but would recommend you get rid, they’re dreadful things, mine always made me cringe when it fired up and ran (seemingly forever) and I mostly only dared run it in the garage with the doors shut!
I doubt you’ll ever silence it effectively because you’ll need to keep an air flow around it otherwise you risk the motor burning out as well as the intake air getting too hot and reducing pump efficiency!
I recently dumped mine and bought a 15CFM twin cylinder compressor on a similar sized 60 Ltr tank, Very quiet in operation even sitting on the drive, even my missus was well impressed (she cringed too when the old one fired up)!
A larger compressor will also fill the tank quicker and run for shorter periods!
Keep an eye on local auction rooms, I paid ?80 for mine including fees and it’s nearly new!
John
PS should have added, it’s the air intake that makes all the racket which isn’t helped by the thin walled alloy cylinder!

Edited By RJW on 26/01/2014 17:30:56

[ChrisHParticipant @chrish]

Yes, it is a direct drive one and I am rather stuck with it at the moment, Senior Management would not approve of further Cap-Ex at the moment, plus I am stuck for floor space, the shop is small and no room available for anything bigger, plus stowage outside is not an option.

I was planning on a closed box with a right angled lined passageway for an air inlet. Martin's foam tiles inside the box might do the trick, will talk to the company first for their advice, but it seems it could be the way to go.

Chris

[Neil GreenawayParticipant @neilgreenaway71611]

Rockwool or saint gobain isover also make varieties of sound insulation materials which could be used inside a plywood wall sandwich. This is available from local building merchants.

Neil

[KWILParticipant @kwil]

There are or at least there were small Hydrovane compressors. . I have one used a spray paint compressor and the same device was used by Dentists to run their drills. Relatively low volumes and pressures though.

[Michael HornerParticipant @michaelhorner54327]

Hi RJW

I have a V twin compressor with direct drive motor and over a short period of time it loses pressure, do you know if this is a built in feature or an air leak?. A guy was telling me it was designed in.

Cheers Michael

[RJWParticipant @rjw]

Michael, can’t say I’ve ever heard of a ‘designed in’ pressure leak off on any compressor, especially over short periods of time, but then I’m no compressor expert!
Mine leaks off over a couple of days, but that’s because I’ve never bothered to check where it’s going even though I can hear a small air leak on the pressure reg’, I just know if I begin fiddling around with it, Sod’s law will dictate something will break and and put it out of action for weeks!
It ain’t really broke so I ain’t going to fix it ;>))
John

[Gordon WParticipant @gordonw]

My small cheap compressor is very noisy, about on it's last legs now, but I don't have anybody near. Just standing it on a bit of scrap wall foam sheet makes a big difference. I made a little shed out of spaced boarding ( Yorkshire boarding) for the outside fan on the heat exchanger and this made a big differance without affecting airflow.

[Ian S CParticipant @iansc]

My compressor was a freezer compressor of some considerable age, when I first set it up, it was noisy, so I made a combined air filter and inlet silencer, it still makes a bit of noise, but not too bad.

You would need to take care if you box it in that you allow enough cooling air around the cylinder, and the electric motor. A revised air intake would be my first try at quietening it. The old machines with a cast iron cylinder and crankcase were quieter. Ian S C

[colin hawesParticipant @colinhawes85982]

I would try lining the box with a thick layer of closed cell foam such as polystyrene with a VERY uneven surface facing the noise source and zig-zag passage in and out for ventilation and stand the compressor on a similar or rubber base. Colin

[steveteeParticipant @stevetee]

I agree with Ian S C almost all of the noise from the compressor is induction noise. If you don't believe me take the air cleaner off , the noise will be deafening. Then try closing off the air inlet with a cork or something…. almost all the noise will have gone. Problem 2 is how to silence the inlet satisfactorily.

P.S. Ian… I enjoyed the Air Force museum at Wigram immensely.

[MikeParticipant @mike89748]

Colin, this uneven surface business reminds me that in the late 1970s I helped cut the sound from a 25-yard indoor rifle range by glueing literally thousands of egg boxes to the walls. It was surprisingly effective.

[RJWParticipant @rjw]

In my dim and distant past as an apprentice, I can remember one of the mechanics digging a big hole under his garage, making a cover out of railway sleepers and shoving his compressor in that so it wouldn’t disturb his neighbours, think he also rigged up a long pipe for the air intake, which itself will cut noise!
Might be worth considering!

[DMBParticipant @dmb]

One place of work a few years ago, they had a printer for a computer. It was mounted in a box lined with black foam with a surface like the bottom of an egg box and a clear plastic hinged lid for access. All seemed fairly quiet until the lid was opened whilst the printer was working. You should have heard the din!! Obviously, someone somewhere makes the egg-boxy black foam. The raised lumps of foam were a lot smaller than egg box domes and therefore, the foam may be a more appropriate size to fit a relatively small sound box.

[lars nelsonParticipant @larsnelson70284]

I built an 8ft x 6ft shop in my bedroom and can run my x2 mill with stock gear drive and my roommates can't hear a thing so I have some success in the area even if blind luck and overbuilding . I'd suggest googling for sound isolation boxes for more info and pictures (if you can avoid getting lost for hours, I can't).

There are 2 things that need to be controlled, vibration and airborne sound waves. Isolate the compressor from the floor of the box with some sort of resiliant material. Make the inside of the box big enough so that there was good airflow around the compressor.

Either line the inside of the box with sound isolating insulation (rockwool) and/or have an inner and outer wall for dead air. Using denser thicker material such as sheetrock, mdf or homosote for the walls will absorb more sound waves than light thin stuff. If using an inner wall try to isolate it as much as possible from the outer wall e.g. staggered studs, box in a box or resiliant fasteners. If doubling up on wall material using resiliant glue like Green Glue would help.

Make sure to seal gaps with caulk and use something like weatherstripping around the access door.

Next we have to deal with the pesky ventilation problem. For that I'd suggest muffler boxes (inlet and outlet)with baffles or corners lined with insulation. Every time sound waves have to change direction there's a drop in noise level so the more changes the better. Put a fan(s) inside the main box at the inlet and/or outlet for air circulation around the compressor. Wire up the fan as is most convenient for you.

Some of this stuff might be overkill but I bet you could build a box 2x2x1.5 fairly cheap, that's just about dead silent with the compressor running, assuming your measurements included room for insulation/airgap and airflow.

As this is my first technical post I'd appreciate questions, constructive criticism and clever snide remarks

[Danny M2ZParticipant @dannym2z]

G'day.

I second the 'egg-box' idea. Years ago one of my soldiers showed me his garden shed. He was an amateur DJ and liked to play the drums. His garden shed was lined with egg-boxes and from outside any noise was just a low rumble. As the 'Housing Officer' I had to respond to a complaint from a neighbour. My report noted that a passing car was noisier, no further action required.

* Danny M *

[Ian S CParticipant @iansc]

steveTee, did you take the tour of the restoration hanger? The museum will expand into the new part once there are a few more large places built for functions that used to be held at the conference centre, but they are not in too big a hurry, it's making money which all museums need.

If you run into over heating of the compressor in the sound proof box, a large ex computer fan could be fitted, if you can, bring the air in from outside, and in the winter the exhaust air could go in the workshop, and outside in the summer, mind you, if your compressor is used as much as mine I'd just have one outlet, mine gets a run every month or three. Ian S C

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