(Soundproofing) Decoupling Your Workbench from the Floor?

[Luke Dupont]

Hi guys. In a previous thread, when I was building my workbench [ https://sawmillcreek.org/showthread....etc&highlight= ], I was given some excellent advise on how to decouple the workbench from the floor, to prevent vibrations from sawing and chopping making it through to the floor -- a huge consideration for anyone living in an apartment:

As for sound……

If you have a neighbor below you then you will need to decouple the bench from the floor with what’s called a floating floor. I own a recording studio and spend my day job making records so suffice to say, I know a wee bit about this stuff. Probably the cheapest and easiest solution is to get a single sheet of rigid fiberglass, like Owens Corning 703 or an equivalent (Knauf makes the same stuff). Get a 2” thick piece. These come in sheets that are 48”x24” so you will only need one since that’s bigger than your bench (you can cut this stuff down with a butcher knife or any thin and sharp and long enough blade). You want to wrap it in something so you don’t get fiberglass on you anytime you touch it. You can wrap it in fabric and just tape the fabric on the underside, some companies make pre-made fabric sleeves for them. You could also just use a black garbage bag in a pinch. Anyway, then you’ll need a THICK piece of plywood or MDF 48x24. Thicker the better – ¾” would be acceptable. Put that on top of your rigid fiberglass. Then put the bench on top of the whole thing. This will provide a stable platform for the bench and will do a VERY good job of decoupling it from the floor without the bench bouncing up and down. So when you pound on the bench, or saw on the bench, those vibrations won’t make it to the floor (well, some still will, but it will be DRAMATICALLY reduced). You can put the fiberglass insulation and the plywood in a coat closet when not in use (rigid fiberglass is fairly dense stuff – don’t confuse it with the fluffy stuff you put in your attic). This also gives you the option to put some cleats on the plywood to keep your bench from sliding around and if the surface area doesn’t provide enough friction with the floor you can lay down some drawer liner. In the music world this is how we keep the drums or the bass amp from leaching into other studio rooms through the floor. Anyway, this is probably the biggest noise problem. Depending upon variables, it’s possible that the plywood could vibrate acting like an acoustic amplifier to your pounding on the bench. If this happens just drop a sandbag on it (needs to be sand because it has to be able to vibrate).

This seems to me like a great solution. However, I can't seem to find "hard fiberglass boards" anywhere, and nobody locally (at your typical home centers here in Japan) seems to have any idea what I'm talking about.

I could order from overseas if shipping isn't too expensive...

I looked up Owens Corning 703 and such, and find it out of stock seemingly everywhere:

https://www.amazon.com/Owens-Corning.../dp/B005V3L834

I found smaller panels that seem to be intended to go on the wall. Does anyone know if these would work? Are they hard or soft? I don't even know...
https://www.amazon.com/gp/product/B0...A35C93BBDX68G6

Likely I just don't know what search terms to use, and also don't know much of the time whether I'm looking at "hard" or "soft" type fiberglass...

Lastly, are there any other options I might consider? I've tried all kinds of rubber isolation / anti-vibration pads to go under the feet of the workbench, but these are terrible because they make the workbench wrack like mad. My bench is quite rigid, but with these pads under the feet, even light planing will cause the rubber to give or deform slightly, thus allowing the bench to move and wrack. I'm guessing that any soft material that compresses will do the same, so whatever it is, it needs to be quite hard.

[Luke Dupont]

Hmm... I wonder if cardboard would be rigid enough, if used underneath a layer of plywood to distribute the weight... Or if it would just get crushed...

[Luke Dupont]

On further investigation, I think these things are too large generally to be shipped overseas...
I even found a listing here in Japan that was "pick up only," which is problematic because I don't have a car...

[Tom Trees]

Lastly, are there any other options I might consider? I've tried all kinds of rubber isolation / anti-vibration pads to go under the feet of the workbench, but these are terrible because they make the workbench wrack like mad. My bench is quite rigid, but with these pads under the feet, even light planing will cause the rubber to give or deform slightly, thus allowing the bench to move and wrack. I'm guessing that any soft material that compresses will do the same, so whatever it is, it needs to be quite hard.

Sounds like you need to sort out the racking problem.
Not sure if you can add some more strechers, or if you can laminate some more meat onto them if you can't do that.

It's the one part of the Continental/Scandi bench which doesn't make sense to me, saying that though, there are many subtle suggestions are to use the lesser timbers or species
for the job, likely as it wouldn't be so bad if you decided to have another crack at it.

If none of that is possible for some reason, then a revamp can use bed bolts instead, should timbers need laminating and mortises need plugged,
and you don't have the time to fill timbers to be as structurally sound as they were before.

SAM_3985.jpg


All the best
Tom

[Luke Dupont]

Sounds like you need to sort out the racking problem.
Not sure if you can add some more strechers, or if you can laminate some more meat onto them if you can't do that.

It's the one part of the Continental/Scandi bench which doesn't make sense to me, saying that though, there are many subtle suggestions are to use the lesser timbers or species
for the job, likely as it wouldn't be so bad if you decided to have another crack at it.

If none of that is possible for some reason, then a revamp can use bed bolts instead, should timbers need laminating and mortises need plugged,
and you don't have the time to fill timbers to be as structurally sound as they were before.

SAM_3985.jpg


All the best
Tom

No no, the bench doesn't rack at all. It's solid. What causes the "racking" is when I put flexible material under the feet of the bench, such as rubber. It compresses and allows the bench to "rack"

My stretchers use tusked mortise and tenons and the wedges keep everything really tight. No problems there.

[George Yetka]

https://www.mcmaster.com/rubber/rubb...rs-and-strips/

Neoprene rubber strips should do the trick

[Derek Cohen]

You want to look up IsoAcoustics Gaia III Acoustic Isolation Feet. These are designed for large hifi speakers. I doubt very much that one per leg would be enough, but it would provide some insight into decoupling, which is big in the world of hifi.

Neoprene and sorbathane do not have the properties needed here. Not in the same league.

Another area to explore are vibration absorbers for washing machines.

Regards from Perth

Derek

[Luke Dupont]

You want to look up IsoAcoustics Gaia III Acoustic Isolation Feet. These are designed for large hifi speakers. I doubt very much that one per leg would be enough, but it would provide some insight into decoupling, which is big in the world of hifi.

Neoprene and sorbathane do not have the properties needed here. Not in the same league.

Another area to explore are vibration absorbers for washing machines.

Regards from Perth

Derek

I've tried the vibration absorbers (the rubber ones, you mean?) for washing machines, and they make the bench tippy / "racky" as they're too soft. I fear the same might be true for felt...
But then, maybe the surface area is just not large enough and I should use more of them underneath a piece of plywood or something to spread out the weight. But that would also increase the contact surface area with the floor and potentially defeat the whole decoupling idea...
Whatever it is, it needs to be hard and not have much "give", or the bench moves too easily while planing.

[Richard Coers]

I suggest you experiment with noise cancellation at the floor and on the bench top. Working on a mat on top of the bench might help cancel at least some of the noise. Your dilemma is you are trying to quiet impact and not vibration that most systems are made for.

[mike stenson]

I'd try the cork/rubber sandwiched isolation pads. Same ones I use on my washing machine and my air compressor. But, I think you're right about the isolation having to be fairly dense.

[chris carter]

I MAY HAVE A BETTER OPTION!!!!!!!!!!

High density foam. I don’t know why I didn’t think of this before. I think it’s because, for decoupling large areas in a recording studio it’s just horribly cost prohibitive so we don’t use it for that kind of task. But we do use it to decouple smaller things all the time. And you should be able to find it at a local fabric store or maybe even a craft store. It’s used for couch cushions, mattresses, etc. I don’t know how popular that kind of furniture is in Japan, but I would imagine you should be able to find it. Here’s a link of what I’m talking about https://www.joann.com/airtex-3-96-oz...m/2162279.html. It’s expensive, but way cheaper than having to import rigid fiberglass. Rigid fiberglass is mainly used as insulation in commercial buildings so for a non-contractor to get it you need to buy it from an acoustics dealer. I know that in Europe it is very hard to get and studios there use something called mineral wool or rock wool. It’s a kind of floppy for your application and I don’t think it would work well. It’s possible that’s what they use in Japan instead of rigid fiberglass.

From a decoupling standpoint, high density foam would work even BETTER. I would go with 3” high density foam which, in the U.S., runs about $50 per yard. If all you can find is 2”, then use that, but thicker is better! You can find it at a fabric/craft store. In the U.S. it’s usually green, but it does come in different colors. Use the exact same application as I described with the rigid fiberglass. It is not so great of an acoustic material for airborne sound, but it is amazing at decoupling. Even better than rigid fiberglass. In recording studios we often use this stuff (not in green color, because it isn’t cool) to decouple studio speakers from their stands or the meter bridge of the recording console (where many studios mount their speakers). This helps prevent the vibrations from the speaker (from the cone moving back and forth violently to create sound) from transmitting into the floor and going from there to another room and up microphone stands and vibrating the microphone. As an additional upside, you won’t need to wrap it in fabric to keep the fibers from coming loose.

Here’s a pic of HD foam in my studio. It has a heavy steel plate on top of it, and then the speaker on top of that. In your case, the speaker is your bench. The steel plate is there for mass and has to do with the ability of the speaker to reproduce sound accurately so ignore that. Although you still need the sheet of MDF or plywood to distribute the load evenly over the foam. MDF would actually be better because of its greater density and mass. The greater the density and mass the lower the resonant frequency (you want as low as possible) and the hard it is to vibrate acting like a speaker. You want as little vibration as possible because that will become airborne sound. You can kill vibrations if necessary with a sandbag or two. My speakers are also on heavy sand filled stands which further decouples them from the floor (basically, there is ZERO vibration at my floor!). Sand is awesome, but I’ve racked my brain on a way to use it for your purpose and can’t come up with a reasonable way to do it.

speaker.jpg

Here’s another shot where I had to keep hard drives on a shelf that is coupled to a wall. To keep the wall from sounding like an amplifier, I threw some HD foam under them. This is the green color stuff you are likely to encounter. The 2” I have here is likely overkill, but I had it so it was free. I will say though, that a 1” piece of medium density foam was not enough decoupling.

harddrives.jpg

Decoupling is a tricky business if you are really trying to silence something. You will NOT be able to silence your bench from your downstairs neighbor as the amount of energy generated from say, chopping a mortise, is insane. But I suspect you could seriously reduce it massively. And I think heavy sawing vibrations could be completely eliminated.

[Luke Dupont]

I MAY HAVE A BETTER OPTION!!!!!!!!!!

High density foam. I don’t know why I didn’t think of this before. I think it’s because, for decoupling large areas in a recording studio it’s just horribly cost prohibitive so we don’t use it for that kind of task. But we do use it to decouple smaller things all the time. And you should be able to find it at a local fabric store or maybe even a craft store. It’s used for couch cushions, mattresses, etc. I don’t know how popular that kind of furniture is in Japan, but I would imagine you should be able to find it. Here’s a link of what I’m talking about https://www.joann.com/airtex-3-96-oz...m/2162279.html. It’s expensive, but way cheaper than having to import rigid fiberglass. Rigid fiberglass is mainly used as insulation in commercial buildings so for a non-contractor to get it you need to buy it from an acoustics dealer. I know that in Europe it is very hard to get and studios there use something called mineral wool or rock wool. It’s a kind of floppy for your application and I don’t think it would work well. It’s possible that’s what they use in Japan instead of rigid fiberglass.

From a decoupling standpoint, high density foam would work even BETTER. I would go with 3” high density foam which, in the U.S., runs about $50 per yard. If all you can find is 2”, then use that, but thicker is better! You can find it at a fabric/craft store. In the U.S. it’s usually green, but it does come in different colors. Use the exact same application as I described with the rigid fiberglass. It is not so great of an acoustic material for airborne sound, but it is amazing at decoupling. Even better than rigid fiberglass. In recording studios we often use this stuff (not in green color, because it isn’t cool) to decouple studio speakers from their stands or the meter bridge of the recording console (where many studios mount their speakers). This helps prevent the vibrations from the speaker (from the cone moving back and forth violently to create sound) from transmitting into the floor and going from there to another room and up microphone stands and vibrating the microphone. As an additional upside, you won’t need to wrap it in fabric to keep the fibers from coming loose.

Here’s a pic of HD foam in my studio. It has a heavy steel plate on top of it, and then the speaker on top of that. In your case, the speaker is your bench. The steel plate is there for mass and has to do with the ability of the speaker to reproduce sound accurately so ignore that. Although you still need the sheet of MDF or plywood to distribute the load evenly over the foam. MDF would actually be better because of its greater density and mass. The greater the density and mass the lower the resonant frequency (you want as low as possible) and the hard it is to vibrate acting like a speaker. You want as little vibration as possible because that will become airborne sound. You can kill vibrations if necessary with a sandbag or two. My speakers are also on heavy sand filled stands which further decouples them from the floor (basically, there is ZERO vibration at my floor!). Sand is awesome, but I’ve racked my brain on a way to use it for your purpose and can’t come up with a reasonable way to do it.

speaker.jpg

Here’s another shot where I had to keep hard drives on a shelf that is coupled to a wall. To keep the wall from sounding like an amplifier, I threw some HD foam under them. This is the green color stuff you are likely to encounter. The 2” I have here is likely overkill, but I had it so it was free. I will say though, that a 1” piece of medium density foam was not enough decoupling.

harddrives.jpg

Decoupling is a tricky business if you are really trying to silence something. You will NOT be able to silence your bench from your downstairs neighbor as the amount of energy generated from say, chopping a mortise, is insane. But I suspect you could seriously reduce it massively. And I think heavy sawing vibrations could be completely eliminated.

Thanks! I'll see if I can't find this stuff. Eliminating heavy sawing vibrations is my number one goal here.
How does it feel to the touch, just so I know if I find the right stuff or not? Is it squishy, or fairly hard and solid?

[chris carter]

Thanks! I'll see if I can't find this stuff. Eliminating heavy sawing vibrations is my number one goal here.
How does it feel to the touch, just so I know if I find the right stuff or not? Is it squishy, or fairly hard and solid?

It should feel soft like you want to lay on it and fall asleep. Like you could jump into a pit of it and laugh. You can also look for a density rating of around 1.8lbs (approximately) and to the best of my knowledge it's always made from polyurethane.

squish2.jpg

Anything you use will have to squish and absorb vibrations in order to work. So by definition it will make the bench less stable (hence the steel plate between the foam and my speaker in my previous post). So when you chop, it will be less effective because instead of the bench reflecting the energy back, it's trying to absorb it. So there will always be a penalty for decoupling a bench from the floor. The trick is to find the right amount of squishiness. If this winds up being too frustrating, you can get a greater density. Something called High Resillience foam is around 3 lbs. I have no clue where you would get that stuff. And then memory foam is around 5lbs. At that point I'd start getting nervous that it might start to conduct more than it dissipates. Additionally, if it's too soft, you can increase the stability of the bench by increasing the surface area. For example, I think your bench is only 2' x 4' or something right? You could make this foam and MDF base 3 x 6 and essentially spread the weight over a greater area. That would increase the decoupling and the stability.

Good luck!!!! You are heading into woodworking uncharted territory. But if you pull this off I'm sure a woodworking magazine would gladly pay your to write an article because I'm sure this is a problem that keeps a lot of people away from woodworking.

[Luke Dupont]

It should feel soft like you want to lay on it and fall asleep. Like you could jump into a pit of it and laugh. You can also look for a density rating of around 1.8lbs (approximately) and to the best of my knowledge it's always made from polyurethane.

squish2.jpg

Anything you use will have to squish and absorb vibrations in order to work. So by definition it will make the bench less stable (hence the steel plate between the foam and my speaker in my previous post). So when you chop, it will be less effective because instead of the bench reflecting the energy back, it's trying to absorb it. So there will always be a penalty for decoupling a bench from the floor. The trick is to find the right amount of squishiness. If this winds up being too frustrating, you can get a greater density. Something called High Resillience foam is around 3 lbs. I have no clue where you would get that stuff. And then memory foam is around 5lbs. At that point I'd start getting nervous that it might start to conduct more than it dissipates. Additionally, if it's too soft, you can increase the stability of the bench by increasing the surface area. For example, I think your bench is only 2' x 4' or something right? You could make this foam and MDF base 3 x 6 and essentially spread the weight over a greater area. That would increase the decoupling and the stability.

Good luck!!!! You are heading into woodworking uncharted territory. But if you pull this off I'm sure a woodworking magazine would gladly pay your to write an article because I'm sure this is a problem that keeps a lot of people away from woodworking.

Ah, I see. So, even with decoupling, it helps to have a larger surface area? I'm always a little bit confused because I thought the goal is to reduce contact area, but it also does seem advantageous to have the vibrations "spread" over a larger area, if you think about, for example, the effect of a hammer on a pin point versus the effect over a much larger surface area, which dampens both sound and impact. This concept has always been confusing to me, making it somewhat difficult to work out what is most effective.

In regards to stability, what I find most annoying when using for example rubber washing machine and vibration pads under the legs is actually not energy lost when chopping so much as the bench moving (due to squishy material under the legs) around when planing. But I've only tried this with single points under the legs, not with the force spread out over a very large surface. Hmmm...

Maybe there are several "auxiliary" devices I can use too, such as benchhooks or saw horses that are decoupled. I'm also making very thin and quiet bow saw blades which seem to help a lot versus thicker saws. Thickness of the kerf seems to translate pretty directly into how loud a saw is. Of course, there's a limit to how thin you go even with a pull saw or bow saw, though. My little Japanese douzuki is just 0.2mm thick, but such a thin blade is far too delicate not to have anything but extremely fine teeth and a back.

I'm curious if the inertia of a very heavy thick bench like a Roubo would be sufficient to avoid this sort of problem when planing. Probably not though.

Well, I will definitely need to experiment quite a bit!

Haha... I should definitely consider writing such an article when all of this is said and done.

All of this said, I am actually currently on the first floor, so this is not as urgent of a problem as if I were above someone. But I've moved many, many times in the last decade and a half, and have been dealing with this problem for most of that time. Also, I've noticed the wooden floor here is "raised" and quite thin, with basically any vibration carrying for quite a distance (I can feel vibrations in my feet), so I'm afraid they may be traveling up the walls. Also, I don't know if I may be moving again soon or not, and could wind up with someone underneath us again.

Anyway, all really great information! Thanks.

[chuck van dyck]

https://isostore.com/product-catalog...RoC9aEQAvD_BwE

This stuff is great. Just make sure you don’t skimp and follow the directions. This with a few layers of lamination will do a lot.