Dampen Workshop Noise With Paper Pulp And Kool-Aid — OH YEAH!

noise dampener

If you’re fortunate enough to have a garage and a workshop, you probably also have neighbors. The truly blessed must work within the confines of an HOA that restricts noise, porch couches, and most types of fun. [Mike] is among the truly blessed, and when he decided to design a cabinet for his CNC equipment, he took noise dampening into consideration.

[Mike]’s design isn’t a blanket noise dampener; it’s specifically designed for the high-pitch symphony of his router, compressor, and vacuum. He also sought to avoid vibrating the cabinet. To achieve this, the sound-dampening panels are hung on eye hooks with a 1/2″ gap between them and the frame. The backer boards are cut from 3/4″ plywood. [Mike] considered using cement board, but thought it might be overkill since he plants to shell the cabinet in a layer of 3/4″ plywood.

The deadening material is paper pulp made from various shredded papers. After soaking the shreds in water and blending the mixture to an oatmeal consistency, he drained most of the water through a cloth bag. Then he added just enough wood glue to hold the pulpy goo together. The tropical punch Kool-Aid powder isn’t just for looks; it provides visual confirmation of even glue distribution.

[Mike] made some tape walls around the edge of his backer boards to hold the mixture in place and painted on some wood glue to hold the pulp. He spread the tropical concoction to 1/2″ thickness with a tiling trowel to avoid compressing it. The peaks and valleys help scatter any sound that isn’t absorbed. Pudding awaits you after the jump.


82 thoughts on “Dampen Workshop Noise With Paper Pulp And Kool-Aid — OH YEAH!

  1. Another even cheaper colorant is actual color, with the added benefit that you can find out exactly what it is and if it will interfere with the glue… I thought “Kool Aid” was a hackaday joke, didn’t think anyone would actually add a drink mix with unknown contents to glue…

    1. You can find out exactly what the powder is by reading the ingredients, it’s right there on the package. A tiny bit of citric acid and salt aren’t going to negatively impact the glue in any noticeable way.

          1. that’s the point, i have no idea what’s in the flavor mix, so i don’t want it in my glue.

            Apart from that, salts and bases/acids can severely affect glues. Why take the chance?

        1. Bigbob; Everyone’s opinion is important. There is no sugar in the packets and for those who say “real colorant” is cheaper, I got the stuff for 20 cents a pack and use one per panel, I have 10 panels in my project so $2 was really no big deal.

  2. Seems like a lot of time and work to go through when you could just buy sheets of foam and cut them to shape… I understand the poverty effort, but how long is this going to last? Most wood glues are organic in nature and tend to start crumbling after a few years.

      1. I grew up building furniture and houses. Wood glue gets maybe 30 years before it starts to turn into powder. That a piece of furniture that is indoors and well taken care, not a garage that will be exposed to the elements.

        1. I actually modeled the sound dampening cardboard idea after a commercial product used for industrial dampening, it was selling for several hundred dollars USD per sheet. The light weight foams are really used for echo reduction in sound recording not for heavy dampening of loud machines. You are quite correct that the shape is very important and that is why I stressed not smoothing out the surface as so many OCD beauty aware makers/hackers would do. The irregular surface is intended to add diffraction and effectively “shatter” a sound wave sending any unabsorbed energy in different directions and reducing the overall impact.

  3. In the daytime folks should be able to make as much noise as they want to. Although I suppose if one wants to pursue a noisy activity at night then some sound proofing might be in order. If you think about it the whole disturbing issue is somewhat ironic. Someone thinks nothing of disturbing someone else, to inform them that they are being disturbed.

    Get off my lawn!

        1. …And someone running loud machinery all hours of the day, every day of the week is going to get repeated noise complaints.

          Just because the majority of the people are awake doesn’t mean you get to bother everyone. Other people deserve to be able to use their yards to entertain friends and not be drowned out by the constant buzz of your stupid tools.

    1. Build in any style you want and paint it any color you want; I can’t care because I don’t have to stare at it. However I can’t escape any noise or odors you might make. Neither can those who work the morning tower. Take such operations to the industrial area where where such noise is the daytime norm, pack along a kitchenette, sofa bed TV etc., you’ll be fine as long as you don’t complain about any nighttime noise that may be the norm as well.
      Stay out of my ears and/or nose.

        1. @pcf11

          I will let you know when there is a house for sale on my street. I live about 30 minutes north of Philadelphia. You can make all the noise you want, until about 10pm, then people care, but it can’t be more noise then my neighbors garage band……

    2. I live in a nice neighborhood with nice neighbors that maintain a quiet atmosphere that I appreciate myself. I doubt my neighbors would mind occasional noise from power tools for projects here and there but I intend to get more routine use of my CNC and air compressor and for long periods of time. I’m just being considerate.

    1. Damping…ug….I wish English weren’t my first language, I’d have a better excuse for that one. Thanks. Dampening = Damping + Deadening….yeah thats what I meant! nope, can’t lie that good. :)

  4. To hell with the neighbors, just to cut down on the noise within the work shop for your own benefit. I know that part of having power tools is dealing with the sound they make but come on! those things are loud and any reduction would make using them a little less taxing in the long term.

  5. White glue and borax would have worked. The borax would serve three functions: cross-link the PVAc (will do this with wood glue too, but that’s thick enough as is), serve as an anti-pest agent, and depending on concentration a flame reatardant; it’s used blown celluslose insulation for properties 2 and 3.

  6. I just built a sound proof enclosure in my dog grooming bus and while I opted to just buy roxul safe and sound for the major deadening part I also learned a few things along the way. One was that mdf is a million times better at sound deadening than plywood. Rigid foam is useless, and a decoupling layer of rubber sheeting or similar is even better than air gaps.

  7. Seems like a lot of work for not much effect (check out the video).

    A much easier choice would be fiberglass insulation with the fuzzy side turned inward. You’ll need something fine-weave (cheap carpet works) to keep the fibers from shedding into the space but I guarantee it will absorb enormous amounts of noise, especially high frequency noise.

    But HF noise dies out in the air quickly, I doubt that’s what would set off HOA alarms. But simply making it airtight will kill most HF noise. He’s also got a low frequency noise problem. That buzz that rumbles out of the space in all directions will be the thing that drives the neighbors nuts. So I have one more trick: leave an inch or two air gap between the paper and the outside wall and it will absorb a ton of low-frequency noise, too.

    I built a recording booth with these tricks and was able to record my guitar amp at insane volumes, even at night, without bothering the neighbors.

    1. Better late than never. I got a weird reminder on this post so I read all the comments again and missed this one. If you check the picture the cardboard red mush is applied to 3/4 ply and those panels are hung on two small wires through hoops at the top so that the mass is basically free hanging and absorbs a huge amount of the vibrational force. Fiberglass isn’t dense enough to absorb much in the way of acoustics and thus the cardboard. There are several principles at play here; 1) irregular surface causes breaking/splitting of sound waves 2) The moderate firmness of the cardboard causes a cushioning effect akin to a good pair of sneakers (not too hard, not too soft). This layer absorbs the sound so it doesn’t just bounce around. 3) the weight of the ply creates resistance which is necessary with low tones and lighter material just wont stop it. 4) the panels are supported on wire so as to reduce the amount of vibration that could travel from the panel into the surrounding cabinet. It works rather well overall and is a bit different in small tight spaces that have no area to disperse the noise. The video was a mix issue for me since I don’t have a real sound tester and used a sound metering app on the phone to try and put some numbers on it but as one of the comments pointed out its because the phone itself mutes loud noises for clarity. End result is the cabinet kills so much of the noise that what is left disperses easily in the garage workshop and you can barely hear it outside especially if the garage door is shut.

      Since the panels are on wires its quite easy to remove them and in a simple wood cabinet the noise, while reduced, is still quite substantial.

      I know it wasn’t your comment but I figured I would state everything in one place but there was a comment of it being flammable and I simply haven’t the issue. In fact not too long after that comment I took a scrap piece and hit it with a blow torch for several seconds without it even blackening so I wont say fireproof but doesn’t seem to be any more flammable than the plywood.

  8. He’s still using the plywood frame of the cabinet as a speaker. I agree, a lot of effort.

    I work next to a big air turbine whose scream is literally deafening. My door is covered by maybe half an inch of foam and then a quarter-inch rubber mat facing the noise. Don’t have more exact information because I’m not at work, but it works like a charm.

      1. Honestly it wasn’t that much effort to make the panels and the cost difference between that and the likely much higher price of the foam you describe is a good reason why I did this. You do bring up a good point on the foam that others haven’t seemed to catch; you are in a professionally designed space meant to reduce sound and the foam they used is “fairly dense , and spongy” not lightweight fiberglass which is better for heat but transparent to loud low noise and not hard and reflective.

  9. Noise dampening. Heh. I’ve been reported as a terroist event. Ah, good times.
    (and no local noise ordanances thankfully)
    Anyway, it looks like he had a lot of fun figuring out a unique way to accomplish what he wanted to.

  10. “[Mike] considered using cement board, but thought it might be overkill since he plants to shell the cabinet in a layer of 3/4″ plywood.”
    Too bad, as weight is one of the components of a good sound deadening setup. Heavy walls will not vibrate as much as light (foam) ones. A layer of foam or other flexible material to mount it to your frame or walls should be there to absorb the vibrations before they transfer into the structure.
    So, if he had used cement instead of glue to bind his woodpulp together I think he might have had something far more useful.
    There is always next time I guess.

    1. He can always just pile more soundproofing material over the paper. Then he could put more on top of that until the room is totally filled. Can’t be noisy if you can’t get into the room to do anything. :V

    2. Cement board instead of plywood would make the sound dampening much better because of weight but I opted against it because I already had a heavy wooden cabinet around it. The panels work on two separate principles with the two layers though, the heavy layer (plywood or cement board) are used to absorb heavy vibrations from lower “shaking” tones and is why the boards are free hung. The cardboard layer is more effective on high freq noise and cant be too firm or it will just reflect the noise making it an echo chamber so I dont think using cement in the pulp mixture would have been a good idea.

  11. You can use foam rubber like used in upholstery, it is very dense and its construction blocks noise well. Speaker makers often use polyfil , sold in craft section for stuffing teddy bears, and that works great but hard to apply to a walled area. Quilt batting is another option, basically polyfil in a roll.

  12. I would have liked to have seen some sort of fire retardant … commercial cellulose insulation is pretty cheap, and is inspected by people who have jobs inspecting insulation (for flammability, pest edibility, etc )… also the most important thing in sound proofing a room from the outside is a mechanical de-coupling of the 2 walls… google staggered stud wall…

    1. I worked with some fireproofers as a laborer once. One guy said the stuff is safe, then started eating it. I wouldn’t consider him a pest though, he was a pretty likeable guy as I can recall.

    2. Gradyplayer; are there any mix-additives or post-install additives you would suggest for flame retardants or are you just saying fiberglass and rockwool only? Just for note; The mix, once dry is fairly dense and although it does burn, does not burn very well but I am definitely not against adding another layer of protection. Also, the reason I hung the panels is the mechanical de-coupling you mentioned.

      1. Stay away from rock wool. That stuff burns! I do not mean in the flame sense either. Rock wool is like the nastiest material from the seventh circle of Hell if you get it on you, or breathe any in. It is so friable it is like weapons grade anthrax that way too. The stuff makes asbestos seem positively benign. I guess when it is not old it isn’t too bad, but it seems to get brittle over time. We called it rotten cotton on the job site. Sometimes we’d go home with our noses bleeding because of that crap. Some of the worst material I have ever had the distinct displeasure to work with. I learned to handle bats of that crap like it was nitro glycerine for fear of getting any of it airborne. I swear it was like someone had a blowtorch and they were passing it over my body. It would get into my pores and then I felt as if I was on fire. I am not joking, or even exaggerating. I can’t even believe that stuff is legal it is so horrible. But I never installed it, I only ripped it out. So I only messed with the old rock wool. I figure new it can’t be as bad as what I’ve experienced. I mean it just can’t be, or no one would install it in the first place.

  13. I’ve built sound deadening cabinets as well but find that fiberglass insulation is the best/cheapest/simplest route – a layer of screen over the open face typically keeps skin contact down and noise damping up, and anything you can do to provide acoustic impedance mismatch (eg. air gap mentioned in other comments – think of a hollow core door and how it really does reduce sound pretty well).

    All arguments and trollage about materials aside, here’s the usual problem, and particularly with compressors as in the video (and eventually CNC machines): heat buildup. The equipment is air-cooled and you have to have air exchange or nearly all of the wattage going in through the power cord is going to turn up as heat in the cabinet. Then you have to provide a cooling fan and/or some ports to manage the cooling, and to damp the sound coming out of *that* you have to get into ducting and baffles. Simple with the HF sounds coming out of a pocket sized CNC mill, but bigger tools not so much (remember 1 Hp = 746 watts, so a 5 hp compressor will turn the cabinet into a sauna and fire hazard in no time).

    Also, think about damping on the feet to get rid of LF noise transmission – nice squishy mounts/material of any sort help here so long as you don’t have resonance in the structure.

    1. I have powered ventilation in the back of the cabinet, it is very important as you say. I’m trying to find a good source for some rubber feet too, do you have any suggestions? Recycled tires? I thought about shoving some rubber wheelbarrow tires under there but wanted something a bit nicer/long term.

  14. I deaden the noise coming through the feet of my generator by placing it on those pads you kneel on they sell at lowes etc. They’re surprisingly stable at high temps and resistant to most liquids. If heat becomes an issue consider an online duct fan of the fantech variety hooked up to a used muffler! Another muffler for an inlet if needed. If you do, pls bend them upward like horns on either side and post a pic lol

  15. I’ve used two layers of acoustic “drop ceiling” tiles for sound deadening. They are really cheap – especially if you buy the damaged ones (crushed corners), and provide a lot of acoustic attenuation.

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