soundproofing enclosures?

discussion of design changes / improvements / suggestions
Llamas
Posts: 201
Joined: Fri Apr 19, 2013 3:36 pm

Re: soundproofing enclosures?

Post by Llamas » Tue Mar 11, 2014 6:28 pm

I don't have any pictures, and the G-code was script generated (as opposed to using CAM software like I do for everything else). My efforts have been limited to square-profile lengths of wood with two stage holes drilled for 1/4" T-nuts (one stage the depth and width of the T-nut insert, the other the remainder of the 1/4" through-hole). On each length I cut a male jigsaw dovetail at one end and female at the other. I just fasten a couple of them together, measure off the length I need for a corner joint, and cut to fit. The remainder starts the next part. These elements are primarily intended to act as connection points for 3/4" MDF panels, which will provide the structural strength and rigidity. I can then remove panels if I need better access to something. Or that's the theory. For my purposes, I probably would have been better served by welding 1/4" nuts to some perforated angle-iron (but CNC router!).

FattyMatty
Posts: 9
Joined: Fri Jan 17, 2014 7:41 pm

Re: soundproofing enclosures?

Post by FattyMatty » Mon Mar 31, 2014 7:38 pm

I thought I'd share my experience trying to soundproof my Shapeoko2 since it seems that a few other people are having the same problem that I did... Neighbours. I'm in an apartment so wanted something that I could stick out on the balcony that would reduce noise and contain dust etc.

My first port of call was to start googling best ways to noise proof things but with so many different ways of doing it depending on what type of noise it is (frequency) and all the different types of materials you should and shouldn't use, as well a contradicting stories, I decided to use some common sense, cross my fingers and do what I think would work.

My main concern was cost, It seems that some of the best materials to use can cost and arm and a leg, proper sound absorbing foam, High density Vinyl, sound proofing drywall were all going to cost way way to much.

Image

I got 90% of the materials from either Home depot of Lowes,

First off I made a 5'x2'x2' frame using 2"x1"

Mounted 7/16 OSB board to the inside of the frame
http://www.homedepot.com/p/Unbranded-7- ... /203408991

Sealed up the seams with green glue, (the only specific noise proofing product I purchased). It took one 28oz tube to seal the insides with a little left over.
http://www.ebay.com/itm/OSI-Sealants-SC ... 565a82df51

Stapled foam padding onto the outside of the OSB board, so that it was in between the framing. (I double this up so that there were two layers of foam which took two rolls of 6x8)
http://www.homedepot.com/p/Future-Foam- ... /203360075

I also used some of this foam on the floor of the box so as to kill any vibration created by the CNC along with an old rubber matting that I had lying around. (this is the black floor you can see in the photo)

You can see by the image that access to the cnc is through lifting the whole corner. The door was created with the same materials and in the same way as the box and attached with three heavy duty hinges.
http://www.homedepot.com/p/Everbilt-3-1 ... 5yc1vZc2ap

There was a slight gap between the main box and the top of the door which is why there is a small strip of foam on the top of the frame, this has been since removed, and I ran some foam tape everywhere the door is in contact with the box to hopefully remove any gaps cause by lack of carpentry skills.
http://www.homedepot.com/p/MD-Building- ... /202066511

I've also attached two latches onto the lid so that it closes it tightly
http://www.amazon.com/gp/product/B007QR ... UTF8&psc=1

I'm still going to cover the outside with some 1/4inch plywood, not only to add another layer of soundproofing, but to cover the foam and once I get a couple of layers of sealant on it it should be able to deal with whatever small amount of rain we get in California.

Now the results... Using an iphone app, (not sure how accurate they are but it's all I had)
https://itunes.apple.com/us/app/splnfft ... 96114?mt=8

In the box with the lid open and approx 2ft away, I measured the spindle at approx 95db +- 4db, this was just with the default shapeoko spindle on the, motors weren't being used.

With the lid closed and latched, it has gone down to 59db +- 5db, this is while the shapeoko was actually cutting into wood so there it couldn't have gone much louder.

In real world terms, this box has been a huge success. I wouldn't even have much of a worry about working on things over night the noise has been reduced so much, it doesn't even bother the wife when she watches TV, no more than 8ft away with the balcony doors open.

As I mentioned before, I've still got the outer plywood layer to add and I'm intending to funnel the wiring/e-stop/on-off switch through properly, but even as it is now it's doing a great job.

I hope someone finds the helpful. I can add more photos or info if anyone else needs anything.

Cheers

janapriya
Posts: 91
Joined: Tue Jan 28, 2014 2:50 am

Re: soundproofing enclosures?

Post by janapriya » Tue Apr 01, 2014 2:06 am

FattyMatty, Please add more pictures. I'm also in an apartment, worried about neighbor complaints.

FattyMatty
Posts: 9
Joined: Fri Jan 17, 2014 7:41 pm

Re: soundproofing enclosures?

Post by FattyMatty » Wed Apr 02, 2014 3:46 pm

Here's some more photos as requested,

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janapriya
Posts: 91
Joined: Tue Jan 28, 2014 2:50 am

Re: soundproofing enclosures?

Post by janapriya » Fri Apr 04, 2014 12:20 pm

Thanks

Llamas
Posts: 201
Joined: Fri Apr 19, 2013 3:36 pm

Re: soundproofing enclosures?

Post by Llamas » Sat Apr 05, 2014 3:45 am

Taking shape. This weekend, top, doors, baffle and wiring.
uploadfromtaptalk1396669512092.jpg
uploadfromtaptalk1396669512092.jpg (37.62 KiB) Viewed 6982 times
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Llamas
Posts: 201
Joined: Fri Apr 19, 2013 3:36 pm

Re: soundproofing enclosures?

Post by Llamas » Sun Apr 06, 2014 1:34 am

My enclosure is 36" deep, to accommodate an extended ShapeOko. Had I not needed that much depth, I probably would have started with a cabinet of some sort from one of the recycled building materials places in the area. They had some promising looking rolling display cases that would have been great had they been deep enough.

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Philip
Posts: 16
Joined: Wed Apr 30, 2014 9:08 am

Re: soundproofing enclosures?

Post by Philip » Wed Apr 30, 2014 3:17 pm

Hi, first time poster, long post :D

I ordered a 1500mm x 750mm eShapeOko a few days ago and I'm worried about noise for the family and neighbors so I've been doing some research. I used to play in bands a few decades ago and had some friends who were actually good at making music; they built a rehearsal studio which is where I picked up some basics.

To successfully isolate a loud noise source (such as a rehearsing band with an acoustic drummer) you need a sandwich of <mass><spring><mass> where the two 'masses' must not be directly connected by sound bridges such as screws. This is basically the 'room floating in a room' principle. The idea is that the vibration is lowered by the inner mass (more mass will vibrate less when exposed to the same energy), the lower vibration has a hard time to pass the springy layer and the energy left after that will hardly be able to make the outer mass vibrate.

The masses should be as heavy as possible, the springy layer should be as thick (wide) as possible. Doors and ventilation are, from an isolation perspective, not allowed ;)

For the mass layers popular materials are sand or (4 or 5 layers of) plaster board while the springy stuff is nowadays usually 'bonded foam', foam plates pressed from flakes of old mattresses and stuff:
Image

I found some interesting information on bonded foam in the following thread. The thread is in Dutch but I only want you to look at the first two images which have English text (those are copyrighted and the author asked not to share them outside his thread), scroll down a bit: http://forum.noiseconsult.com/viewtopic.php?p=4037

Since the spindles we use produce noise in the 2000kHz(?) range the right side of the images is most important. The first image tells us that a layer of bonded foam with a thickness of 50mm and a density of 80kg/m3 gives the best isolation results in our range while the second image tells us a heavier density (=more expensive) does not much improve the situation. Therefore my conclusion is to best use bonded foam with a density of 80kg/m3 and a thickness of 50mm as the springy layer.

To create a double box for my size of machine I roughly need something like 2x1x0.5 meters, which needs (if my rusty math is correct) 10m2 of foam and 2x10m2=20m2 of mass. I was able to find sheets of bonded foam with 80kg/m3 and a thickness of 40mm for €11 per m2, so that would set me back around €110.

If I look at plaster board the m2 price is in the €6 ballpark so that would be 6x20=€120 *per layer*, times 4 layers is €480 :shock:

That made me look at sand, because you can basically scoop up a few bags anywhere outside and is anyway very cheap when bought.

So here is a rough outline of my future design goal:
Make a box of 2x1 meter and 0.5 meter(?) high out of plywood, open at the top. Lay a layer of sand on the bottom with a thickness of 50mm. On top of that lay a layer of bonded foam which leaves an area of 50mm around the edges exposed (for the vertical outer sand layer). On the edges of the foam I glue the vertical layers of foam. Make a rectangle of only the sides of the inner box out of plywood and rest it on the foam with an area of 50 mm left open around from the vertical foam (for the inner vertical sand layer). Poor a layer of 50mm of concrete on the foam that is still visible inside the inner box and let it cure. Make a plywood bottom on top of the concrete and attach it to the inner box; this is where the machine will rest on. Finally, gradually so the foam won't sag, put sand in the open spaces on both sides of the vertical layer of foam. Then create a double lid out of plywood, foam and plaster board. You still with me? 8-)

This should work quite well if my information is correct. Problem still to solve is possible heat buildup.

Anyway, I happen to have about 2 m2 of bonded foam with a thickness of 1 cm left over from some carpeting we did. I guess at some moment I will make a small box in the way described above where I can put my mini guitar amplifier into (15x10cm) and make a test run. This will take a while though.

Cheers!

Llamas
Posts: 201
Joined: Fri Apr 19, 2013 3:36 pm

Re: soundproofing enclosures?

Post by Llamas » Fri May 02, 2014 11:20 pm

I found a few examples out there of people building enclosures for air compressors, which generate a fair amount of waste heat. They all resorted to the use of fan-driven ventilation through baffles lined with sound deadening/diffusing material.

It will be interesting to see what the sound levels are like when using different enclosures. What does it take to hit certain levels of sound reduction, and to what lengths do you need to go in order to get to that next noticeable level?

I started out with a cabinet inside a cabinet design, but I'm building a single cabinet first. If it's good enough, I'm not going to the extra effort to go from good to better. I'm not sure the sand and concrete aspects of your design lend themselves to half-measures, so I can't suggest the same approach here. How quiet do you need to make things?

--Mike
Perfect is the enemy of Good.

Nigel K Tolley
Posts: 226
Joined: Sat Feb 08, 2014 4:06 pm

Re: soundproofing enclosures?

Post by Nigel K Tolley » Sat May 03, 2014 10:15 am

I did a judging thing many years ago, where different types of sound proofing were tested by a group of school kids.

Various options were tried, like glueing on packing peanuts to the outside of a cardboard box.

The best option for the lowest money was simply two boxes with an air gap.

Don't forget also that you can line the inside of the box with high density thin PU foam (like a gym mat) which helps a lot as it really boosts both sound absorption and the mass of the inner box. And is cheap!

You could also do the outside of the outside box, though that is diminishing returns probably.

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