Enclosure - most bang for the buck in noise reduction

Hi everyone

there are many great videos about enclosures for CNC machines. Some work incredibly well in reducing noise. Those all have in common to be huge, heavy and take a lot of work to build. Which makes it difficult to remove when working on larger peaces of wood or for maintenance. Apart from different designs i’m wondering what’s the best bang for the buck in terms of noice reduction.
Basically the more mass ist being installed (wood, rockwool, plastic etc.) the more noice can be isolated.
My questions now is: with how little material can i get the “most” noise reduction effect?
For example: 1 layer of 18mm plywood already reduces … 50%? A second layer then another 20% and so on? Or does it more stack up like 20% the first layer of wood, another 20% the second layer etc…
Has anyone got some experience in that field?
Thanks for your knowledge and experiences!

Hey Pascal,

many build an enclosure from thin plywood birch, which results in something that vibrates like a guitar or piano body, i.e. you prevent a little airborne sound when it’s tight, but it vibrates and makes spread sound anyway. The best solution, as for speaker cabinets, is to use MDF panels as thick as possible, but then that’s a pretty bulky thing, and to take care to seal it completely.

But besides using an enclosure and perhaps soundproofing material that absorbs mainly airborne sound, the best sound decoupling is that of structure-borne sound, which would be by preventing a separate inner enclosure from having a resonant bridge to the outer one. I say this because I have been studying how a table or an enclosure can also prevent structure-borne sound, that is, the vibrations that do not come directly through the air, but go into the floor and into the building.

By the way, what I find important in an enclosure is that the door and the top of the enclosure is not in the way when you lean over the worksurface to do your clamping. I like this one, but not for noise reduction. The main purpose of a CNC enclosure is protection from flying debris of broken bits, which can be very dangerous.

But that is just a thought. I hope others contribute their experience, as I’m still not ready with my enclosure plan.

What we used to sound damp the engines in the yachts we built was a product which is a layer of lead with a layer of spongy foam on the back, very effective.
For a low cost alternative I intend to build my enclosure using thin plywood with a layer of foil faced insulation glued to the inside. Halo exterior foil faced insulation is one flavor, best if the foam is a bit soft.
The science is that the foil surface is moved by the sound waves but does not transmit it to the plywood.
Last time I priced the Halo brand it was about $30 cdn per 4x8 sheet.

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If sound was an issue for me I would just make a simple box out of rigid foam panels. Simply lift the whole thing up (or maybe make it in two pieces) to get access and then set it in place when cutting. I would put a couple plexiglass windows in as well as some LED lighting so you can see how things are going. A webcam would be nice.

I’m installing 2 layers of sonopan and 2 layers of drywall in my enclosure. I’m about halfway through install. I’m hoping it reduces the noise.

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With an X50 Journeyman that would be quite a box size. Since i have little space in my workshop i need to integrate it into the enclosure.

Yes, i’ve seen in this video: https://www.youtube.com/watch?v=HMU4V2S-feM that the effect is quite strong. But i’m also surprised about how well 3/4" plywood did on it’s own!

The enclosure I’m going to build will be this one here: https://www.youtube.com/watch?v=BNyxC3mZCXo and with 22mm thick MDF the noise reduction should already be quite good. I’d install less windows and not sure wether to add a second layer of foam/sonopan on the inside tough…

Also to reduce the noise produced through vibrations i’m thinking of a “sandwich” construction for the tabletop plate like 18mm plywood, sonopan and another 22mm of MDF. Then glued together with a silicon glue insted of screws. then attaching the plate from the bottom with screws only through the MDF. that might kill most vibrations and still be a very stable surface. what do you guys think?

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That looks good! My enclosure is going right beside my work desk in my basement. I’m going to use the exterior drywall as a secondary wall. I might mount a cork board or a white board to it. I’m putting a small bulkhead in the back as an air intake tunnel. Fein vac is under the table. I’ll add an enclosure for that if it’s too loud.

I’ve just watched several videos on the principal of sound waves moving through air, walls etc. And one of the best ways to isolate, is in theory to hang a second floor/wall on springs which will absorb the vibrations and sound. they will loose then the energy in the springs and almost nothing gets to the other side. as that is very difficult to realize in an enclosure, the version with the foil gets very close to that! so thumbs up for that solution!

I found in Switzerland a “Bitumen Heavy Foil” which they say to suppress 30db of noise when used in the 5.5mm version. Perfect to keep the enclosure doors and walls slim and still have a huge noise reduction. They are heavy tough. Combine that with a 21mm MDF and i’m sure that “in theory” 40db reduction should be feasible with not more than a 3cm thick wall! And the best: It’s not going to cost a lot of money: The foil is around 40$ per m2.

i’ll post some photos and a video as soon as i’ve created the enclosure.

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It was explained to me that the inner surface works best if it has mass and is also dense, as this tends to respond to the sound waves minimally, (Hence the lead we used in the old days) So I would think that a layer of plywood would be excellent if it could be adhered to any material that would support the weight and not pass the sound waves through, so a soft foam or even mineral wool or FG insulation would suffice, Would not put an open layer of FG or mineral wool inside the box because of dust retention becoming perhaps a fire hazard. Then the construction of the outerbox can be quite light but the more detail put into the insulation layers the better.

Hi guys

For once i can give some experience back to the community. Here is the enclosure that i built for my Journeyman. I ordered the upgrade kit to the Elite Version and everything should fit in there too. But i‘ll know for sure in 6-8 weeks time :wink:

The basic design is from mitz. I just adapted to my possibilities here in Switzerland. Enclosure is made entirely out of 22mm MDF. Heavy and cheap. Inbetween i added Bitumen-Plates for more Vibration Reduction. The DB reading is 10cm right in front of the plexiglas while cutting 0.8mm finishingpass while beeing 26mm into the MDF wasteboard.
I havent got much space or hight in my garage so i had to move the table mm by mm to get the most out of it and still being able to open or close the garagedoor :wink:

The shopvac is hidden away in the cupboard below.

Hope that gives inspiration…







Oh and here is the DB reading with the enclosure open at the same milling job/position

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I waited until my neighbor went to work and then set up my CNC in his basement and then changed the lock on the door. It’s super quiet in my shop and house now.

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