Workshop sound absorption panel effectiveness

Hi Everyone I am finishing up a small workshop with a concrete floor, plaster skimmed block walls and a 3m/10ft painted OSB ceiling. Right now the space is empty so it feels more live\louder than it will once full of machines cabinets etc but still clearly it needs something done about the acoustics.

I have been looking into sound absorbing panels of various types (melamine foams) and it appears that while they would be easy to install and not too expensive they are most effective with frequencies over 2 kHz while my research indicates that the bulk of the spectrum produced by manual machines (a couple lathes, a manual mill with max 6.5k rpm) and those sorts of things is below 2 kHz. Having a physics background I am well aware of the wavelengths of lower frequency sounds (on the order of meters) and the fact that foam is going to do nothing to attenuate them. Does the higher frequency attenuation still make a significant difference in terms of comfort etc? It does seem that high frequency noise is more annoying than lower anyway.

Does anyone have experience as to the most effective way to acoustically treat a workshop space? Or should I just wear earplugs all the time which I should probably be doing anyway


thanks

Luke

If you're that concerned about accoustics, just wear ear plugs. Or, put a stereo in the shop and turn it up to 11.

whidbey said:

Hi Everyone I am finishing up a small workshop with a concrete floor, plaster skimmed block walls and a 3m/10ft painted OSB ceiling. Right now the space is empty so it feels more live\louder than it will once full of machines cabinets etc but still clearly it needs something done about the acoustics.

I have been looking into sound absorbing panels of various types (melamine foams) and it appears that while they would be easy to install and not too expensive they are most effective with frequencies over 2 kHz while my research indicates that the bulk of the spectrum produced by manual machines (a couple lathes, a manual mill with max 6.5k rpm) and those sorts of things is below 2 kHz. Having a physics background I am well aware of the wavelengths of lower frequency sounds (on the order of meters) and the fact that foam is going to do nothing to attenuate them. Does the higher frequency attenuation still make a significant difference in terms of comfort etc? It does seem that high frequency noise is more annoying than lower anyway.

Does anyone have experience as to the most effective way to acoustically treat a workshop space? Or should I just wear earplugs all the time which I should probably be doing anyway


thanks

Luke

Click to expand...

Some questions:
1. What is being done there ? Wood working, metal working, welding, etc.
2. What rules must you follow ? Commercial shop with fire codes, home shop, basement shop, etc.

I would suggest first to try some cheap ceiling tiles made into 3-d pyramids or "v" shapes, hang from ceiling.

Out of the way of welding sparks etc.

BUT not good for a smoke filled oily environ.

also, try scrap carpet pieces hung freely (maybe 12" wide) on ceiling.

Have you looked at the sonex website ?:
Acoustic Foam & Soundproofing Panels - Sonex Online
Industrial Applications for Acoustical Panels - Sonex Online

This is something I've been looking into for a while, as I hate having my shop being so loud that I have to wear ear plugs... My goal is to get the shop to the point where it's under 70db all the time, slowly making progress on that.

Personally I would stay far away from any of the foam panels. Even the 'fire retardant' ones still aren't all that great when exposed to sparks/flame, and they are really hard to clean and get torn up easily in a shop environment...

The best acoustic panels I've found for shop use so far are the ones from 'Singer Safety', they are quilted/non-woven fibreglass panels and are rated for exposure to the sources of ignition you would find in a regular shop:

Double Faced Quilted Fiberglass Panels | Singer Safety Co.

Northern Tool sells the silver versions and the prices are actually very reasonable, cheaper than the equivalent foam panels actually! The sound absorption curve for these panels is also more suited for workshop use than foam panels. The absorption peak is low at 250Hz, but the transmission loss peak is higher at 4Khz. Full data is here:

SC-124 | Singer Safety Co.

I haven't bought these yet as I've only just recently found out about them, but I will likely be buying a few within the next couple of months. They will be used to line the wall behind my VMCs to cut down on reflected noise, and then the enclosures of the machines themselves will be damped with a butyl product designed for damping panels in cars. I have already done the panel treatment on the spindle enclosure on one VMC and it reduced belt noise by 12db which is a HUGE difference!

-Aaron

Look up anechoic and do the calculations for sound absorption and reflection. You should be able to attenuate the higher decibel frequencies to a level comfortable for human hearing. Use C Filter when measuring Sound Pressure Level (SPL). SPL meters are quite inexpensive and you won't need a calibrated meter if you buy new.

Not sure if this will help but this is what we did here.

2x6 framed walls on 24" centers, cavities filled with rockwool insulation, horizontal strips of wood and then finally 5/8" drywall.

My spaces are fairly small as far as big shops go, they are sectioned off into no more than 4000 sqft halls about 40 feet wide.

Ceilings are 6" spray open cell foam dyed black.

No echo in any of the rooms with equipment, we have two that are empty and have very minimal echo.

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If it were my task, I would load things in and begin operations, and use a spectrum analyzer to see where your problem areas are.

Then, look up Helmholtz resonators to absorb narrow frequency bands, and the various other wideband products mentioned for the rest of the issues.

Also, consider structure-borne impact noises (that can cause entire planes to become radiators) and deal with them at their source, with properly-spec'd isolators. X-attenuation @ Y-frequency (band) with Z-weight applied. Mason Industries or Peabody Kinetics. Note that this may fly in the face of the 'bolt everything down' approach, or seismic concerns. Although there are constrained isolators that will work for seismic.

Finally, basic rubber mats can have some positive effect on the floors, if your workflow will allow them.

This is a very small space (300sqft) just for small (mostly Schaublin) manual machine tools in rural France so anything goes in terms of materials although I obviously don't want something that is a fire hazard or is going to collect dust too badly. There room is nearly a cube given the high celling and small floor area which I think is particularly bad for reverberation. I have some software I can use to model the behavior/gain but need to find the right materials to model.

The quilted panels are interesting but I will have to see what is available in Europe.

There are some panels made from wood fiber and cement that look great but they are super expensive "designer"products you would find in new concert halls and not really in budget.

A sandwich of alternating density materials (foam, bitumen, foam) would be great but those are crazy expensive in my experience.

EDIT

waiting until the shop is setup is probably wise. I am just stuck waiting to import my machines from Norway so I am looking for things to do in the meantime.

Luke

Tall ceiling height is good, because it gives you room to hang large absorbant batts up high, breaking up the soundfield. That is, if you can get the lights below them.

It's also where all your heat will go in the winter, so maybe plan for some reversible fans, or heat chimneys, to get the BTUs back down to where they'll do some good.

Well if it's in France, might as well surrender and give up on having good sound in the shop.

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Several of the suggestions above are to reduce sound transmission. What the OP said he wants is to cut noise within the shop; not to stop annoying those outside.

Best way to deal with that noise is at the source -- easier said than done. If there is motor whine, line the motor cabinet with an appropriate sound deadener. If a saw is noisy, seek a smoother and quieter cutting blade. As one example, I built a box with a leaded foam liner to enclose a particularly noisy rotary phase converter. Worked fine to trap it at the source.

Not sure there's either much noise or much to be done with a Schaublin lathe or mill other than have sharp cutting tools running with proper feeds, speeds, and lube.

If it's an unavoidably noisy operation, ear plugs or ear muffs are the best option. While some folks really like to work with music and noise cancelling headphones, I personally feel that hearing ambient noise (without music directly in your ears) is safer. I do like music in the shop -- but it's from speakers far enough away I can still hear the operation in front of me.

Acoustic tiles, foam, carpet, baffles etc. can reduce reflected noise at higher frequencies and little effect at low frequencies. They can help a bit - especially with speech intelligibility within the shop. And, the OP's small shop with nothing but hard surfaces will reflect pretty much everything. Rock wool behind a perforated panel or mesh is one approach that is relatively fireproof. Might help to place it especially where higher frequency sound first reflects from an operation.

Used to be that audio spectrum analyzers were expensive. Now a phone app can give decent info to guide and check alternatives.

I'm thinking out loud here....12" and 8" dia. sonotubes (cardboard tubes for pouring cement for the OP)
4' long pieces, glue carpeting on inside.

hang these up horizontally (and maybe vertical)
Should keep most dirt from them, lower frequencies enter thru ends.

Shiny cardboard exterior doesn't get dirty, and don't terminate hi frequencies.

For what you're trying to do, I would look at Owens-Corning 703 or a similar compressed fiberglass product. Stick it behind walls with open slat construction and if you can stick 6" thick units across as many corners as you can spare for the low frequencies.

The will kill a lot of the echoing but obviously won't stop the initial impulses (ear protection may still be required).

I'm typing this from my home recording studio where I have similar treatment, but set up to make the listening location as "true" as possible. Walking in here is spooky the first time since there is little to no perceptible echo. I also have the benefit of a "perfectly" shaped room for its size, so the more of a cube you've got the worse you are for certain frequencies.

Good luck, keep us updated!

The schaublin mill (a 13) is loud at high speeds thanks so straight cut gears and maybe some wear so I use ear plugs with that machine and with other noisy operations
Machine noise is only part of the issue, a room that is too "live" just isn't comfortable, this is a lab or office as much as it is a machine shop.

I will do some measurements once it is set up and play around with different solutions.
L

Here is a link to perforated panels used in a shop:
Perforated panels mean silence

You can also put rockwool or similar on the wall and cover it with boards, just leave a gap between the boards so sound can get behind them. (like Rick mentioned above)

I have been looking into this as well and read somewhere that cubicle walls are sound absorbing. Do you have cubicle farms in France? If so they should be cheap or free if you know anyone remodeling an office space....

those fiber cement panels are in fact rather cheap if you can get them at the building materials dealer.
try leroy merlin or bricodepot

OK, I have done a bit of this before.

2 issues...

first is direct noise from a machine.

second is noise reflected from walls

For the first, you put absorbing material between the machine and where you want less noise.

For the second, you put the material near the wall. The thickness of material applied to a wall makes a difference, BUT, you also can simply space it out from the wall to do better.

middle C on a piano is a wavelength of around 2.5 feet, close to a meter. The most air movement (which is what you want to cut) is at 1/4 wave from the wall, since at the wall there is no movement, it is a "node".

So for anything down to about middle C, you space the stuff out from the wall 6 to 8 inches. The insulation material is good, but needs to be compressed to 2 or 3 x regular density. Wire mesh and some thin bolts to hold it together will do the squashing of the material to a tighter density.

You need quite a few of them, and may be better off to hang panels up from the ceiling with some north-south and spome east-west. That will do the job with fewer panels.

This works out in front of the machine for direct sound also, but you still get reflections of whatever sound did not come that way.

Best is to do the walls, and then cut the noise at the machine if possible by direct sound absorbers.

I've dealt with shake testers in a big echoing room, and similar. Best there is to put the panels around the machine (studio people call them "gobos") to cut the noise at the source. Then you may not need a lot more.

Otherwise, hang or apply near the walls.

thanks janvanruth, Any idea what they would be called in French I have tried a bunch of different terms without finding quite the right thing. (I do know you are unlikely to have French as a first language but yours is going to be better than mine I can find wood (wool) fiber insulation but that is without the cement binder. I can find BAUX from Sweden which isn't exactly inexpensive (around 200 euros per square meter which is a bit much for wood fiber and cement pressed into a sheet) I have considered making it myself, I think I would just need to find a good source of pre-shredded wood and stick that in a mixer with water and cement and pour it into a form of some sort.

whidbey said:

thanks janvanruth, Any idea what they would be called in French I have tried a bunch of different terms without finding quite the right thing. (I do know you are unlikely to have French as a first language but yours is going to be better than mine I can find wood (wool) fiber insulation but that is without the cement binder. I can find BAUX from Sweden which isn't exactly inexpensive (around 200 euros per square meter which is a bit much for wood fiber and cement pressed into a sheet) I have considered making it myself, I think I would just need to find a good source of pre-shredded wood and stick that in a mixer with water and cement and pour it into a form of some sort.

Click to expand...

sorry but i wouldn't know what they are called in french
heraklith makes them
2.5 cm strong is about 25 euro per square meter in Holland.

I worked for a company which had a TV studio right next to the room where the heating equipment was located. The boilers were LOUD and the pumps were also. They had a professional acoustic consultant come in and they recommended some quite expensive panels to be mounted on the cement block walls. They installed about 10 or 12 of them, covering well over 50% of those bare walls. It worked to a point, but as is stated above, these panels were better at absorbing the high frequency sounds and not so good with the low frequency ones. Frankly, a sound proof door which sealed on all four sides, did a lot more for the problem. But that equipment still had to be shut down while shooting in the studio.

I guess my point is, even the most expensive panels will be of limited use with low frequency shop noises.

You can get the acoustic foam pieces with those wedges that you see in the "sound proof" rooms. I believe these work better than flat panels simply because they have more exposed area. And they reflect less sound back into the room.

AURALEX Sound Absorption Panels, 12" Width, 1 ft. Length, 0.50 Noise Reduction Coefficient '('NRC')' - 458J14'|'WEDGIE_24 - Grainger

And I totally agree with the idea of going after the sources first.