Drum set and a brick wall - reducing noise with a PARTIAL barrier/panel

ditto
and add a drum isolation pad is about as good as its gonna get on the cheap.

Oh,and that "plaster" thing is most likely parged stucco.

G
 
sasquatch and mixsit, huge thanks to both of you. I've been banging my head on my hand here as people just keep repeating that "soundproofing" and "acoustic treatment (traps, etc)" are completely different things not related to each other, I'm an idiot who just doesn't get it, and my mind has been going: @#¤*dammit... YES - THEY - ARE! They ARE related! (and I'm not an idiot)! This is what I'd almost call a breakthrough here, now I feel I know I understand something so going forward is much easier.

mjbphotos: You suggested making a bass absorber? I must have totally missed that part in all the confusion. Yeah, I could do that. Would it work if shaped like that though? Most bass traps I've seen are very deep or wide (much more than 4") and placed exactly in the corner and that's the worst place for anything large. Actually there are some old crates in the corner right now, and I would like to get rid of them. They're almost touching already so I can't expand the right side of the set with for example another floor tom (and I'd want that possibility back).
Concerning the reflections, I don't want to lose the cymbal sounds. Back when the place was basically covered with old rugs and blankets all over, the set sounded horrible and off balance (frequency-wise) because the highs were missing. I'm also under the impression (and there are several medical doctors in my family) that it's low frequency sound that really damages your ears. A loud cymbal sounds like it would be worse than a tom or something but as far as I know that is not actually true and it's the other way around. I'll have to double check that. I've been following that rule of thumb for 20 years and my ears are fine (the last time my hearing was tested, beep test, was over 10 years ago but I actually played the drums much, much more in those times (and was in a rock band). My hearing was normal with nothing out of the ordinary noted. Don't have any more tinnitus now either.

Since I already have almost all of the wood stuff I'm going to use, and most of the soft stuff as well actually... I could do a really rough comparison just by recording something, then placing the wood (unsupported) against the wall and recording again. My gut tells me I'll like the wood surface MUCH more. To be a little more technical, consider wood as a material in general and consider the type of wood. Wood is nowhere near as strong or hard as concrete, and especially untreated wood is porous aka it's a diffuse surface. Maybe a studio with walls covered in thick lacquered ebony (or even oak) plywood panels would be "too reflective". However, what if the wood used is pine instead? And it's thin beadboard left unpainted? You probably already see where I'm going with this.
Bottom line, no practical wood (oak, or birch for example are hard and dense -- and very expensive) is "hard" in this context. But like I said, I have the opportunity to even actually try different things so let's see. I'm not going to do that very many times for sure.

That's a good suggestion in any case though, so thank you mjbphotos.

sasquatch: I must have sat here too long... "and add a drum isolation pad"? Add what, where? What are you referring to?

Thanks to all of you again. I'll be back with more, I'm sure.
 
Uuuuhm... one more thing.

This was touched on previously. What happens, vibration-wise if I take a piece of polyester foam and hammer it to the wall with a 9" nail? When (and if even) people say that the one tiny nail on a several metres wide wall will transfer vibration and ruin the isolation (and insulation), are they being serious?

I mean, instead of a regular wall plug (which are already soft plastic), I could use one made of silicone or some other softer material. But I'm not convinced it matters THAT much, and I can do it without any wall plugs at all. This sounds also like something purely academic. I'm sure the nail does transmit vibration but it's SO small that is it even possible that a nail (well a bunch of nails, or screws) would actually be a concern?
 
If the difference between a wall and a bit of timber is audible in reflectance, seems odd to then flow the other way and believe that coupling won't be audible. You can of course use a soft substance like silicone, trouble is it isn't much use at holding things up, which is after all the purpose!

Surfaces of any construction other than perfectly flat have a link to frequency. Anything absorbed cannot be reflected, so the idea that porous wood not being a good reflector holds water (sorry, couldn't resist) but the practical result is that higher frequencies will reflect very well, with the reflection decreasing as frequency lowers.

I can't help wondering if you could try a very simple test before you build anything. How about getting a sheet of marine ply in the full sheet size, and set it up in your room where your device would sit. Have a play with it, and move it around, and even try coupling it to the wall and see the sorts of differences that appear. Cheap and pretty easy to implement. It would help you make decisions on where to go?
 
spitzer said:
mjbphotos: You suggested making a bass absorber? I must have totally missed that part in all the confusion. Yeah, I could do that. Would it work if shaped like that though? Most bass traps I've seen are very deep or wide (much more than 4") and placed exactly in the corner
Click to expand...

Yes, standard bass trap construction - typically people make them in 4"x2'x4' size because that's the size of the OC703, 705 or Roxul batts, but no reason you can't make it to the full size you need - except that the smaller ones are easier to move around, stack, hang, etc.
 
rob aylestone said:
If the difference between a wall and a bit of timber is audible in reflectance, seems odd to then flow the other way and believe that coupling won't be audible. You can of course use a soft substance like silicone, trouble is it isn't much use at holding things up, which is after all the purpose!

Surfaces of any construction other than perfectly flat have a link to frequency. Anything absorbed cannot be reflected, so the idea that porous wood not being a good reflector holds water (sorry, couldn't resist) but the practical result is that higher frequencies will reflect very well, with the reflection decreasing as frequency lowers.

I can't help wondering if you could try a very simple test before you build anything. How about getting a sheet of marine ply in the full sheet size, and set it up in your room where your device would sit. Have a play with it, and move it around, and even try coupling it to the wall and see the sorts of differences that appear. Cheap and pretty easy to implement. It would help you make decisions on where to go?
Click to expand...

The short answer to almost everything in that post is: no. ;)

1. I am not intending to attach timber directly to a concrete wall, like I've expressed multiple times. BTW, wall plugs are soft. Unless you think the vinyl/nylon/whatever they're made of is harder than concrete? Or brick? Or the steel screw inside them?

2. Yes, the intention is that the higher frequencies will remain. Also keep in mind that beadboard is beadboard, so it has "slats" in it by its nature which makes it... ta-da, a diffusor. I'm not really sure to be honest how the microscopic pores by themself would affect sound, but wood is wood and as a whole significantly different than concrete in every way.

3. Why not, that's a solid suggestion. I would probably already have tried that with my gobo, if it wasn't stuck (yes literally stuck) between a bunch of gear. I can't transport anything that big though, and it would be a needless expense as I already have the woodstuff I need. And more actually.

I still haven't decided what to do with the random collection of random sized pieces of chipboard and something that I'm not even sure what it is. It's definitely not chipboard, it's harder and heavier but it's not regular plywood either. Something like hard fiberboard or cross-laminated timber? Old closet doors as far as I know.

Thanks Rob.

I did a simple test of another sort. I placed a small (15"x15"x7" roughly) cardboard box on a stool about one metre in front of the drum kit. I put two small pieces of entry mat (felt on rubber, you know what I'm talking about) in there, as well as three small (smaller than the box) pieces of chipboard. So what I accomplished, in theory, was a very small barrier panel with a one inch thickness in chipboard. The rest of it was cardboard, which I'm sure is not an effective sound reducing material. So there is plenty of "flanking" involved here.

I placed a mic (SDC, shockmount) behind and inside the box as best I could manage, pointing through the barrier at the drums. Note: one major flaw here is that there could still be vibrations transmitted through the floor since I couldn't find anything to further float the mic stand. So it was just the rubber toes on concrete. The drums are standing on two separate mats, which significantly reduce vibration but don't completely eliminate it (which is something I'm going to have to look into later). I recorded about 15 seconds of me playing the bass drum and floor tom, as hard as I could (and much harder than I would if it was a musical context). First with the barrier, then removed the barrier without even touching the microphone and played the same thing again.

Anyway, quickly, what I found out was that even this stupid little box was effective in reducing/altering the sound on the other side of this barrier. Amplitude-wise, I got a reduction of 0.54 dB (average) and 2.55 dB (peak). Now, what's more interesting actually, is the frequency distribution. What I got there was this (bass drum):

without barrier: largest peak between 70-140 Hz (-30dB), 35 Hz barely there (-52dB) . 70 Hz at -29dB.
WITH barrier: largest peak between 150-300 Hz (-31dB), 35 Hz even lower at -54dB . 70 Hz at -34dB. (if anyone knows how to "tt" (monospace AND preserve whitespace) this, please advise!)

So the frequency distribution was significantly altered and the low and even very low frequencies were attenuated, significantly.

I don't have (or I'm unaware of these features in what I have since I've never needed them) software right now to do a more thorough analysis. The frequency spectrum of the entire 15 second clips for example is something I can't readily do (software suggestions? something free preferred). I also had the mic's gain setting very low and had to boost it a LOT. New mic, new interface... testing those at the same time and had to "eyeball" the gains and pads. Clipping would have ruined it for sure so for this, I got usable data at least.

To sum it up, after doing this experiment... I'm not more, but probably just as skeptical/cynical as I was before concerning flanking in particular. To me, this screams that you don't need a complete wall the size of seven passenger cars to get effective sound reduction.
 
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What do you guys think of polyurethane (sheets/blocks, used as thermal insulation in housing for example) as an absorbent material in a trap? The Internet Web Search Service says the density is comparable to that of commonly used rockwool. Which brings me to another thing, but I don't have time now.

I'll be back with more.
 
To sum it up, after doing this experiment... I'm not more, but probably just as skeptical/cynical as I was before concerning flanking in particular. To me, this screams that you don't need a complete wall the size of seven passenger cars to get effective sound reduction.
Click to expand...

Sound reduction ......... where? All I can say with certainty, from using perspex drum screens is that once you but a barrier close to the source, it gets louder at the playing position. Drummers always say the volume goes up when they first experience screens, and the spill into other mics goes up too. At the other side of the screen, it gets quieter - the desired result. This is not flanking - which is a physical connection that passes sound, not an air path. A wall plug is designed to be solidly mechanical - it works by compression in the simpler types - the screw into the softer than wall material plug expands it, making it MORE rigid than it's neutral state. This creates the path for vibration to follow into the new structure. I thought this was pretty straightforward. The types that provide physical strength but less scope for vibration usually do it by their shape allowing flex in one plane and rigidity in another. A freestanding obstacle always makes it quieter behind it - we're arguing about how much it absorbs. Keep in mind that if it is packed with anything capable of absorbing sound, then this absorption only impacts on what got through the initial layer. If the layer is 100% reflective, then the absorber has nothing to do, does it?

You are so absolutely certain your idea will work, the only way to prove it to yourself is to build the damn thing. So far, nothing you've said convinces me it will do anything other than reflect the drum sound. If this is what you want, go for it. If you hope it will stop sound leaking out of the room, I think you will be disappointed.

Are you hoping it will be a reflector, or an absorber, or a bit of both? Do you want it to be wide band in it's performance or narrow band, focussing on specific frequencies? I really can't follow the thinking processes here. I've tried and failed. There seems a constant trickle of new information being added - now we're onto polystyrene instead of rock wool. There is plenty of material out there on the differences these two make in audio terms - rock wool seems to win.
 
mjbphotos said:
Never heard of polyurethane for thermal insulation. Link please. Likely to be as expensive as rockwool.
Click to expand...

I refer to Rob's link above (thanks Rob! That's good info). Interesting you've never heard of it. PU is outwardly similar to styrofoam (EPS, XPS) which I'm sure you have heard of. As expensive as rockwool? ...what's your point?

The reason I mentioned it is that I happen to have a couple of panels of that stuff (well, one, but I'm not entirely sure if it's two of them just glued together. Used to sit in a corner that for some reason was leaking heat). Didn't think before now that they might be applied for acoustic purposes also. I'm also interested in the XPS and EPS stuff. None of these are particularly expensive, in fact EPS panels are slightly cheaper than rockwool. Harmless to handle, cut, carve or whatever and much thinner than rockwool (for the same amount of thermal insulation anyway). Similar density.

rob aylestone said:
Sound reduction ......... where? All I can say with certainty, from using perspex drum screens is that once you but a barrier close to the source, it gets louder at the playing position. Drummers always say the volume goes up when they first experience screens, and the spill into other mics goes up too. At the other side of the screen, it gets quieter - the desired result. This is not flanking - which is a physical connection that passes sound, not an air path. A wall plug is designed to be solidly mechanical - it works by compression in the simpler types - the screw into the softer than wall material plug expands it, making it MORE rigid than it's neutral state. This creates the path for vibration to follow into the new structure. I thought this was pretty straightforward. The types that provide physical strength but less scope for vibration usually do it by their shape allowing flex in one plane and rigidity in another.
Click to expand...

Sound reduction on the other side of the ONE particular wall, like I have said countless times. Presently, the wall surface is CONCRETE. It is HIGHLY reflective and in a way that I do not like. Can you understand this much?

It's irrelevant what you thought was "pretty straightforward", wall plugs are not the point.

A freestanding obstacle always makes it quieter behind it - we're arguing about how much it absorbs. Keep in mind that if it is packed with anything capable of absorbing sound, then this absorption only impacts on what got through the initial layer. If the layer is 100% reflective, then the absorber has nothing to do, does it?
Click to expand...

Any obstacle makes it quieter behind it. I'm not sure what you are arguing about.

You are so absolutely certain your idea will work, the only way to prove it to yourself is to build the damn thing. So far, nothing you've said convinces me it will do anything other than reflect the drum sound. If this is what you want, go for it. If you hope it will stop sound leaking out of the room, I think you will be disappointed.
Click to expand...

You keep saying that I'm absolutely certain about something, while I'm not, and have not claimed to be.

What is this "it" you're talking about? Seriously. What are you referring to? It's something in your head. I don't know what you are talking about. I am here asking for advice on how to best achieve what I want to achieve with what I have and what I will get. Do you understand? There IS no finalised plan, I'm making it as we speak.

Are you hoping it will be a reflector, or an absorber, or a bit of both? Do you want it to be wide band in it's performance or narrow band, focussing on specific frequencies? I really can't follow the thinking processes here. I've tried and failed. There seems a constant trickle of new information being added - now we're onto polystyrene instead of rock wool. There is plenty of material out there on the differences these two make in audio terms - rock wool seems to win.
Click to expand...

This is all because you skip crucial pieces of information that have been provided, misinterpret things and make your own bizarre assumptions. You only seem interested in telling me again and again that YOUR twisted vision of what I'm planning will not work. And that is useless information to me.

You can't follow, because you don't follow. I have at no point suggested using rockwool for anything.

I have specified in detail what the device (which does not yet exist) is supposed to do. I have answered your questions already. To answer them again: I don't care WHAT it will be, and obviously focusing on specific frequencies.

Other people here haven't had major problems understanding the issue, or the basic concept. They have NOT seen the need to make it more convoluted and confusing than it needs to be. They have also provided simple, practical solutions that are sometimes a bit different and mutually exclusive with the original idea but that is fine, to an extent. Like I have said countless times. And I have learned a lot during this time, which is GREAT. I hope others have learned also, which is most probable since only a handful of people have taken part in the discussion but the thread has been viewed well over a 1000 times.

Rob, respectfully, if your intention is not to help me design this thing I'm not sure what is. But I do not want to argue with you about this or that. This is not an academic debate. I am NOT interested in nor do I intend to prove any point to you. I will readily admit (and already have) that I am not an expert in room treatment, acoustics, physics, materials technology, or construction, or indeed most things in the world. I have never claimed to be. Do you regard because of that I'm someone of low intellect? There's a reason I'm asking you this particular question.

The plan keeps evolving. BTW, I now have a bass trap. I have not yet decided how this will change the placement or design of "the device". As a reminder, THE most significant part of this entire thing is to transform the relevant part of the concrete wall into a WOOD wall, if I haven't stressed that enough (the very first idea I had did not involve an absorbtion component at all).
 
I have been following this thread since I first made suggestions, I am totally confused as to whats going on.

I thought that you wanted to reduce the noise level in the next room and to make the room you are in sound better and quieter.

However every suggestion made you seem to answer with a different idea that you think will work. I can tell you I have built many rooms and there is no shortcut.

If you want to reduce noise into the next room the wall between the rooms needs to have mass added or another wall built off it. It needs to cover the whole wall. Decoupling the kit from the floor using wood on top of some sound deadening sheeting will also help.

If you want to reduce the sound level in the actual room you need to treat the room with bass, mid and high treatment. Forget the perspex screens, if you put anything around the kit use some gobos with treatment on them.

Alan
 
witzendoz said:
It needs to cover the whole wall.
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This was precisely what was debunked previously. It was the breakthrough point. When sound is absorbed, it is not possible for it to leave the room. Thus it can not be heard on the other side of any wall, door, or even a gaping hole.
 
Also, my cardboard box experiment clearly showed that even a VERY small barrier blocks sound. Some of it could have been absorbed there as well, but that's beside the point. You do not need an entire wall, period. If you did, how could gobos work?
 
Sorry maybe I misunderstood it came up in post 22, 49 and 52 so I though you were considering it.

I think this whole thing has become too complex and too hard to understand because every time there is a suggestion you come up with an argument that something else will work. I can tell you if you want to play the drum kit in the middle of the night you need to sound proof the room. Forget absorbing the sound within the room, even though reducing the room liveness can reduce the sound level within the room it will not sound proof the room. Any gaps out of the room will transmit sound out of the room, any week points in the room construction will let sound out of the room.

Alan
 
witzendoz said:
Sorry maybe I misunderstood it came up in post 22, 49 and 52 so I though you were considering it.

I think this whole thing has become too complex and too hard to understand because every time there is a suggestion you come up with an argument that something else will work. I can tell you if you want to play the drum kit in the middle of the night you need to sound proof the room. Forget absorbing the sound within the room, even though reducing the room liveness can reduce the sound level within the room it will not sound proof the room. Any gaps out of the room will transmit sound out of the room, any week points in the room construction will let sound out of the room.

Alan
Click to expand...

I'm going to have to look VERY hard through this entire thread to find an instance of that.

There is an enormous misunderstanding already there that causes the following: what you tell me is of zero importance. Reason: I never said my intention was to play a drum kit in the middle of the night.

I NEVER thought or said any of my ideas would reduce the sound (amplitude) to the other side by more than a few, 2 to 5 decibels possibly.

I NEVER said "reducing the room liveness" would "soundproof" the room.

I NEVER said anything to the contrary regarding "gaps" or "weak points", I never discussed them at all. If you want to discuss that, I can assure you there are no gaps in a brick wall that is surrounded by 10 cm of hard plaster concrete on both sides. I'm not going to discuss that though, since I see no point in that.

Alan, are we on the same page now? Do you have more suggestions of things I need to forget?

Here's the thing: like I said, and added to my edited first post, very simply I am only "treating" the wall partially no matter what. That is not going to change. The only thing of any interest is HOW am I going to it. What exactly am I going to do. I don't know that yet, which is why I'm trying to come up with different ideas and wondering IF they would work. This is very distinctly different from claiming that something will work. I have not, and CAN not make such claims concerning a device that does NOT EXIST!!! (even metaphysically, since I DO NOT have an exact plan of anything)

With respect.
 
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