View Full Version : Reducing noise during run with box enclosure

07-02-2015, 08:00 PM
I want to reduce as much noise as possible while the machine is cutting into work. I hope to achieve this through enclosing machine into a unit out of wood and have these soundproof pads attached inside all-round (http://www.ebay.co.uk/itm/Self-adhesive-Acoustic-Soundproofing-Fire-Proof-CLASS-O-FOAM-Marine-Narrow-Boat-/141308232353?pt=LH_DefaultDomain_3&var=&hash=item20e6a082a1).

Ive got a basic 540 router and want the wooden box to surround the whole unit with a acrylic panel at front for viewing. a vacumm hose will also be inserted through enclosure

any suggestions on whether this is best for noise reduction? thanks

07-02-2015, 09:15 PM

If done correctly then it will make it a lot quieter. But there are some things to note -

The wood is a barrier to stop the noise getting through, but needs to be fairly well sealed otherwise it will only be partially effective. I assume you will add a door, and if so you need to add seals to it. I think 12-18mm ply would be fine for the box, or you could use MDF. Whatever you choose the heavier the better.

But in creating that barrier there will now be much higher noise levels next to the machine, due to the reflections from the new walls, therefore you need to line them with absorption materials such as the foam you linked too. Otherwise you won't get all the benefit.

The best absorption materials are blended fibres but these are expensive. The cheapest absorption materials are recycled felt type, but these are not very effective. In the middle are PU open cell foam types similar to the one you linked to, which still work well. The class 'o' fire rating is nice to have in case the worst happens, but does add to the cost. Given the frequencies you are trying to absorb I'd go with 20-25mm thickness.

The acrylic viewing panel is of course a good thing to have, but acoustically it will be a weak link because it will be of a much lower density than the wooden panels. You could try with say a single panel screwed to the inside of the wooden door and see if it is quiet enough - but provision for a second acrylic panel to be screwed to the outside of the door. Two acrylic panels seperated by an airgap (i.e. the hole cut into the door) will give more noise reduction than the sum of their individual effects.

If you just poke the extraction hose through a simple hole in one of the sides lots of noise will leak out. The simplest solution, and the one I'd go for, is to screw a metal flange adapter to the inside and outside of the hole to make a sealed pass-through. If you try this and it is still not quiet enough you will need to consider making a silencer, which is a bit more work.

In summary:
Wooden box of at least 12mm ply, ideally 18mm - sealed at all joints, including around the 'door'
Lined with PU open cell foam, class 'o' fire rating (as per your link), of at least 20mm thick
Extraction via a pair of metal flange hoses on the inside and outside of a hole in the wooden side

That should make a big difference to the noise levels.

08-02-2015, 07:18 PM
yes I was thinking of adding a door but it was just going to have a single acrylic panel. Might make it a double panel if noise still seems to high. should I add the sound proof panels on the router near to the z axis plate mainly or in other key places?

I dont have have a metal flange handy so il try attaching a plastic pipe in between that I can find spare.

Im running the router in an office suite as I'm trying to do this hobby on the side and don't have anywhere else. This is the key reason for reducing noise.

09-02-2015, 06:47 PM
Absorption depends on the area of reflecting surfaces covered, in a reasonably linear way, so don't waste material trying to cover the Z axis as it is tiny in comparison. You need to cover a reasonable area of the inside walls of the enclosure as per your initial post.

How much you choose depends on your pockets as the costs do add up, but somewhere around 80% of the side and back walls should make a big difference. If you do the roof as well then it will be even better, but secure it really well as you don't want it falling onto the machine.

The acrylic view panel will be reflective but there is not much you can do about that.

Don't know the size of extraction pipe, but the flanges for 100mm are quite cheap (2.75 ea) - use one on the inside and one on the outside with silicon sealant under the flange for a sealed pass-through:

12-02-2015, 07:43 PM
thanks for the help.
i best get started then. will have pics posted up soon on outcome.