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

spitzer

New member
I'll add more detail later (not too much later I hope). Anyway, a simple concept and a simple question to start with. I'll say right now that I'm looking for just a slight improvement and I'm not going to do a TON of work.

So, there's a drum set in the corner of the room right next to a plaster cement (part plaster, part cement, on the harder side so de facto, concrete) coated brick wall. On the other side is a bedroom. The issue is twofold: attenuating the sound getting through to the bedroom and making the acoustics a little nicer (obviously the drums sound... a certain way with a VERY hard wall on one side and lots of air on the other side of the space).

What I'm thinking is basically building a 2 m long, 1,5 m tall, 12 cm deep (7 ft x 5 ft x 5" for the Empireans) panel. It will have a 2"x4" frame, and the outermost layer is beadboard. I also have extra chipboard I can use for something if necessary. The panel would be attached to the wall right at the corner, with felt, carpet or something else underneath to dampen vibrations. The inside of this panel is going to be filled with something, which is an unknown at this time. Ideally something that would also make it a bass trap/low frequency absorber. I edited this to reduce the confusion I for some reason caused by first saying I would "basically nail a wooden box to the wall". Which is still 100% true, but most everyone misunderstood it to mean something totally different than what I actually intended. I changed the topic for the same reason.

Ideas on this concept? I will mention that I am aware of flanking and such things, BUT I don't think they're that important here. I left an SPL meter in the bedroom and from there, it registered a max of 60 dB [*] in the current circumstances, so like I said I'm looking for a SLIGHT improvement, not complete isolation. Before anyone mentions it, floor vibrations are already handled.

If anyone has information on which way a drum set primarily projects the sound, that would be appreciated. I'm unable to do a complete "sweep" of that kind myself. The bass drum alone with the mic one meter in front of it gets me peaks between 90 and 100 dB with "typical loud" kicks. Years ago, I did register 142 dB (!) from above a snare drum but that was a very loud hit not really within normal playing dynamic ranges.

And regarding this box/panel, what would maximise low frequency attenuation within these constraints? Keep in mind that these aren't exact plans at all, I can make it slightly bigger, I can make it slightly thicker, I can increase the air gap a little bit, but I don't want to make it excessively big. The room is small enough as it is. I have a little bit of extra chipboard lying around that I could use, currently it's actually just in the way and at least I'd have more floor space even just nailing them to the wall! :)

Thanks in advance.

[*] That was hitting the kick, floor tom and snare only. I was purposely concentrating on the low frequencies (snare solely because even though it's HF, they tend to be loud).


I realise this is a very complicated an extremely unconventional solution
, I don't need any reminders about that. Also, since it's an unbelievably frequent suggestion: I am NOT going to treat the entire wall. Period. Please understand this. I'm interested in and would hugely appreciate any information that would maximise the performance of what I am actually going to do. Please understand this is also an experiment. And please understand that if it completely fails, I will have no trouble dismantling it and doing something else in it's place. I am completely fine with that. I am not interested, AT ALL, in suggestions to do something else, I'm interested in the science and mechanics of THIS concept and this concept only.

Best wishes.
 
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mjbphotos

What?!?
Nope. You're making a resonating box that way. Build out a frame with 2x4s and stuff it with OC703, 705 or Roxul Safe & Sound. Somehow get it to stand a few inches AWAY from that brick wall - touching it will allow the sound to move from the wood frame into the brick wall. This secondary wall needs to stretch from one side to the other in front of the brick wall, not just where the drums are.
 

witzendoz

Senior Member
Why not put another layer of plasterboard over the plaster wall before you start, if you do it with a sound block plaster board, which is higher density, it will reduce the sound through the wall. I had a friend in an apartment block that had trouble with the TV next door, did what I said here and can now hear nothing from next door.

If you are covering it with a full acoustic panel after you don't even need to finish it or paint it, just fill the gaps.

Alan.

Have a read of this.
 

spitzer

New member
Nope. You're making a resonating box that way. Build out a frame with 2x4s and stuff it with OC703, 705 or Roxul Safe & Sound. Somehow get it to stand a few inches AWAY from that brick wall - touching it will allow the sound to move from the wood frame into the brick wall. This secondary wall needs to stretch from one side to the other in front of the brick wall, not just where the drums are.

Building a full-sized second wall is not possible in this case (btw, your suggestion also requires the 2x4's or whatever it would "stand" on to touch existing structures allowing vibrations to propagate). However, I get the feeling you possibly misunderstood something about my concept (I suppose a diagram would help a lot).

It would not be a "resonating box". The wood frame would not be directly touching the brick wall, there'd be some sort of softer material inbetween (possibly a rubber bottomed canvas carpet like I mentioned). Also, the panel from the inside would not be smooth, hard reflecting surfaces on every side. The "box" would contain some type of absorbing material. Would I nail a huge, empty wood crate to a stone wall and somehow expect it to absorb sound. ??? No, that's not the idea. Besides, even if I did that, there's no way I could make the massive BRICK WALL resonate MORE than it already does. Is there? Nothing passive I put on the wall is going to amplify the sound that's heard on the other side!

I am convinced there is a way to achieve a decent result just developing the concept I have now. mjbphotos, I think at this point there is too little information for anyone to flat out say it won't (theoretically) work.

Remember, the SPL is pretty low on the other side as it is. Reducing it by just 3-5 dB or something like that would be completely satisfactory.

I'll keep reading about the subject, but so far I haven't seen even an academic reason anywhere for why my idea would not work. A physical barrier is a physical barrier, it will block sound from getting through.

P. S. This is also an experimental project for me. It doesn't matter if it doesn't do exactly what I hoped it would do. And I have to do something to that stone wall, like I mentioned it's horrible even if only considering the acoustics of the room.
 

spitzer

New member
Why not put another layer of plasterboard over the plaster wall before you start, if you do it with a sound block plaster board, which is higher density, it will reduce the sound through the wall. I had a friend in an apartment block that had trouble with the TV next door, did what I said here and can now hear nothing from next door.

If you are covering it with a full acoustic panel after you don't even need to finish it or paint it, just fill the gaps.

Alan.

Have a read of this.

Thanks for the link, could be useful.

Could you be slightly more specific? Are you, like mjbphotos, also talking about covering the entire existing wall? Just that you suggest plasterboard and in general something simpler.

My original idea actually had nothing to do with soundproofing, only improving the acoustics. I thought I would basically just nail some planks to the wall in that corner (like I said, the reverb that close by from a concrete wall is nasty...). Then I thought well, why not try and add a little soundproofing at the same time, won't really be much extra work.

Just a simple extra layer of plasterboard might indeed work just fine. I am interested in how things with air gaps work though, that's why I had some questions in particular about that. But I have to again stress: soundproofing the entire wall is impossible. Infeasible to the point of being impossible to be more exact but you get the point. That is not going to happen.

Another thing came to mind. You know those acrylic screens drummers sometimes play behind in some wacky situations? They do not completely seal every side of the drum set nor do they have a ceiling, but they do reduce the volume to the outside. No 2x4's necessary. Those screens must be horrible for the acoustics, but I'm betting the barriers don't need to be clear plastic for sound attenuation (despite the "flanking" everyone likes to talk about) to work.
 

witzendoz

Senior Member
Were talking different things here, there are acoustics and soundproofing.

I was suggesting another layer of plaster board as you wanted to reduce the sound to the bedroom, and I also suggested sound barrier type plaster board, it is double the weight but almost the same thickness as normal plasterboard, the sound rejection of this board is much better than standard plaster. I have 2 layers of this on the walls and ceiling of my studio. The extra layer will help with the sound into the bedroom.

Now with acoustics, you could build yourself gobos to place around the kit to reduce reflections from the walls, I would also make some broadband absorbers for the walls and build a bass trap or two. Al this you can make very easily and there is a lot of discussion on various threads here on how to do it.

Alan.
 

spitzer

New member
Oh, I suppose the first time I mentioned "plaster" could be ambiguous. There's no plaster board on the wall currently, it's plaster (mortar) coated . Aka a concrete surface. Different things in that respect.

I understand the difference between acoustics and soundproofing, my project is a little bit of both. I have a gobo as well but it's elsewhere in the room.

I'm not looking to treat the entire space [*], only that one specific spot is problematic (acoustically from the inside and less, much less from the other side, from a soundproofing standpoint) and most importantly I'm not going to invest a lot of time and money into anything at this time.

I'll try to make a diagram. Depending on things, that could be after I've done my little experimental panel (kind of like a gobo actually) though.

Still interested in a) specific spatial directions in which a drum set mostly projects low frequencies and b) how to maximise LF absorbtion in any system incorporating an air gap.


[*] The other parts of the room are already treated in various ways. Generally, the room is pretty diffuse, and works well enough for what I need. Only the one harsh, flat wall is any kind of problem (and it even depends on who you ask if it IS such a big problem).

Thanks. Later.
 

rob aylestone

Well-known member
Leaving the structure chat to others, I wonder if you've thought about practicalities like volume in your cube? We hear stories from drummers made to play in perspective boxes on stage, and these are rarely six sided like yours will be. The volume inside a contained area that small will be immense. It will also get hot and smelly very quickly with such a small volume in M2. My drum room is a room within a room and the only thing I can hear outside it comes through the shared concrete floor, and is the kick drum. It runs through structure very easily. The usual solutions to your problem use mass. Each time a layer is passed through level drops, and the loss is less as we go lower until we get left with the really low end. I can't see a simple solution to your problem but a small box is a horrible way to ray to sort it, because it probably won't work,mans will be nasty to be in.
 

mjbphotos

What?!?
Ok, you didn't mention filling your 'box' with anything in the first post. You said the floor vibrations were already taken care of, hence my suggestion of a full secondary wall.
Why can't you cover the whole wall? Any area you leave untreated/uncovered will be a path for the sound to go through.
Planks on the brick wall will reduce sound transmission a little, but won't help the room's reverb much, if anything - just change the timbre of it.
 

spitzer

New member
rob: I have, thought about practicalities I mean. I wonder though what you mean by "an area that small" since I don't think I wrote any of the dimensions here. I know what you mean about the kick drum. I'll just say that playing only the drums is not a big problem at all volume-wise. 60 dB peaks in the bedroom is not bad. The opposite wall, which leads outside is extremely massive. The volume is substantially lower on that side.

mjbphotos: I know doing the entire wall would be better but it's not feasible. There are many, many reasons. But it's pointless to go into detail since very simply, I am not going to do that. I'll throw some pointers in case you're merely interested: plumbing, electrics, very high ceiling.
Btw, changing the timbre is one of the main acoustical points here. I don't wan't a concrete wall, I want something softer and/or more diffuse.

Check out this link, the part titled Panel Absorbers. Low Frequencies
That is the kind of thing I'd like more knowledge and possibly experiences of.
(and yes, yes I know that is not the same thing I described. But that's much more in the right direction. Please, forget the suggestions about "room within a room" and double walls. I'm completely aware of what they are, but I'm not interested in those kinds of things right now.)

Thank you for your input.
 
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spitzer

New member
...
I would also make some broadband absorbers for the walls and build a bass trap or two. Al this you can make very easily and there is a lot of discussion on various threads here on how to do it.

Alan.

Missed this earlier... so... pretty much what I was thinking about to start with (a-b-s-o-r-b-e-r-s) can be made very easily and there are lots of instructions here on how to do it? But most people say that will not work and I should do something completely different. I am confused. :confused:
 

witzendoz

Senior Member
Broadband absorbers do not sound proof the room, therefore do not work for that, but they do take a lot of bad frequencies out of the room, highs and mids, therefore making the volume inside the room less on the ear and making the room sound much better.

Most studios around the world have broadband absorbers in the room. They go hand in hand with bass traps.

Alan.
 

spitzer

New member
Wait, what? It absorbs [*] the sound, right? So what will it not work for?

These are "stupid" questions to some, but I am reading a TON of contradictory information from different sources.

[*] ~converts the sound energy (air pressure) to heat
 
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witzendoz

Senior Member
Wait, what? It absorbs the sound, right? So what will it not work for?

These are "stupid" questions to some, but I am reading a TON of contradictory information from different sources.

It's because the question is 2 questions,

So, there's a drum set in the corner of the room right next to a plaster coated brick wall. On the other side is a bedroom. The issue is twofold: attenuating the sound getting through to the bedroom and making the acoustics a little nicer (obviously the drums sound... a certain way with a VERY hard wall on one side and lots of air on the other side of the space).


To reduce the sound into the bedroom you need to thicken the wall or build a separate wall with an air gap.

Making the acoustics nicer are things like broadband absorbers and bass traps.

You also asked about What I'm thinking is basically building a roughly 2m x 2m wooden box (2"x2" support frame, chipboard, planks, don't really know yet) and nailing it to the wall next to the drums (rubber bottomed canvas carpet against the wall before the panel).

Which most agree wont be a good solution.

If the people answering the thread took time to read the original post the answers may be more consistent. I was also saying that making the room sound nicer with some absorption will reduce the sound level in the room due to there not being sound bouncing around the wall, which will make it nicer to play in. If you want an example, set a drum kit up in a gymnasium with hard surfaces and hit the snare, then set the same kit up in a venue with carpets and furniture, which room does the snare sound loudest in.

Where was this stated? Missed this earlier... so... pretty much what I was thinking about to start with (a-b-s-o-r-b-e-r-s) can be made very easily and there are lots of instructions here on how to do it? But most people say that will not work and I should do something completely different. I am confused.

If you want to see answers that are not contradictory read some studio design books and articles. I own a couple of books on the subject and have build my current studio (4th studio I have built) using advice from these books.

Alan.
 

spitzer

New member
...
If the people answering the thread took time to read the original post the answers may be more consistent.
...
Alan.

I was just thinking about that... did I omit some kind of crucial detail about the situation since people are answering, but they are answering completely different questions than I asked and I'm not getting the information I'm looking for. Somehow this has turned into some sort of debate, but about a totally different topic.

I've worked as a teacher myself so I know this is very difficult most of the time. But (one thing) that I would really appreciate is if someone would explain why my concept would not "work". What exactly would it not accomplish? Furthermore, no one has even asked me further details of the design. How can you say something will not work when you don't even know what it is?

I have other interests as well but my time is as limited as everyone elses I suppose. You have been most kind and informative, Alan. Thank you.

I'm considering posting a diagram (the difference between my assumptions/expectations against the consensus here seem to be too fundamental though for it to be of use). I'm also considering an altogether different concept, which I think could also be adequate. I'm thinking on my feet here, that's another thing why proper feedback and discussion (instead of statements like "no, that will not work") would be so nice.

Respectfully.

EDIT: And oh. Guys. I just actually did think of something I did not mention that is maybe not crucial, but important. You could, and should keep in mind that my place is not a professional level recording studio, and is never going to be. This is especially relevant when it comes to acoustics. Any treatment I do is going to be cheap, DIY, leftover materials, etc.
 

spitzer

New member
sasquatch: thanks for the tip! Mattresses are too big though (I don't want to shrink the wall by much more than 5 cm) and... hmm. I'd actually have to check but I think they would be quite expensive actually. That's actually somewhat close to my latest idea, which would use less wood and more other stuff.

The other day I watched a video where a guy soundproofed his drum studio by hanging curtains on the walls. Curtains. And it worked. And yes I do mean soundproofed, not just acoustics. The SPL outside dropped measurably by almost 10 dB, from 65 to 55 roughly.

I don't remember if I mentioned this, but whatever I end up doing is going to be experimental. But I'm actually interested in the science behind this stuff. That's why I've been asking these questions, that's why I've been reading articles, that's why I started this thread in the first place ! If I wanted something stupidly basic and something "everyone knows" definitely works, I would just DO IT, not type a bunch of stuff here.

Respectfully.
 

rob aylestone

Well-known member
No he didn't. we've gone back to the two different but connected terms - sound proofing, as in keeping sound in, preventing leakage and preventing outside sound leaking into the space, and sound treatment that makes being inside the room sound good and consistent as you move about - diffusion, reflection, absorption with no concern with how much sound makes it through or gets absorbed because that's what the soundproofing then does. Sound on sound magazine use duvets all the time to control the sound in a room before they work out what the problem is, and source the correct solution. SPL dropping 10dB really doesn't mean very much without a frequency to put it in context. Some medium to heavy weight curtains could happily reduce the HF content passing through them, but do hardly anything to the kick drum or low toms. No point getting upset with the replies because you will NEBVER get consensus on these matters. I'd like to think I'm quite knowledgeable, having built quite a few studios, each one better than the last, but I've had some of my working ideas poo-poo'd by the real experts because while they worked for me, my circumstances helped the solution work in my example and in a different one would have failed. In some of the published material - like this wonderful book
https://www.amazon.co.uk/Home-Recording-Studio-Build-
Like/dp/143545717X
- you find that some of the things I have always done make minimal difference, but other things have major impacts. I;d suggest you buy the book for details, the science and specifics. Curtains do not soundproof a room. They just don't. They have an effect on transmission. 55dB isn't silence. 10dB from 65dB is lower - it's just a meaningless measurement and totally subjective. You can build a vocal booth that has no leakage of sound at all, but stick a bass amp in there and it leaks like a sieve. Context is everything. even though our suggestions seem to argue with each other, they're probably all valid in people's experience. After all, how many people build a studio one way, then knock it down and try it again to compare the difference? I tended to take practical approaches, using a measurement mic and a pair of headphones and going around my room within a room looking for leakage, and I found it in plenty of places - often not where I expected. On my second studio I had the idea of filling the room up with smoke from a smoke machine, then looking for it leaking out. It did find door seals and gaps where the ceilings met the top of the walls, but most came out of the air extraction duct. In the book I linked to it mentions windows, and how little extra reduction you get from each additional sheet of glass - yet we spend ages putting in extra layers. Other info is contrary to common sense. I just don't understand why you're cross with the responses - what exactly did you want people to say? Your original question - 2m x2m box nailed to the wall was just a crazy idea that pretty well everyone unanimously said don't do, because by attaching it to a wall compromises the acoustic isolation, and I think you know that really. You said
If anyone has information on which way a drum set primarily projects the sound, that would be appreciated
The physics of a membranophone is that they produce a coherent wavefront, which is a perfect couple to an unsupported panel at some frequencies - so clearly a drum parallel to a wall panel between joists will induce sympathetic movement in the panel unless it is well damped, has sufficient mass and rigidity to resist movement. With the kinds of SPL from a kick drum, it's not hard to imagine the panel moving. Worse, the energy has rot go somewhere, and if the panel is rigid, then the support of the walls and ceilings can pass the energy onto the next structure. To be successful you need mass, physical strength etc - but above all - distance, which in your 2m cube you do not have. Inverse square law allows energy to drop off quickly as distance increases, but in a small room, far less so - so that energy is constrained and more difficult to stop. Best of luck - I suspect, to borrow a phrase from BBC TV's Dad's Army - you're doomed!
 

spitzer

New member
rob aylestone: Thank you for your detailed post, I don't have time to read it thoroughly right now, I need to go for 2 hours.

I will say though, that I do understand the difference between soundproofing and acoustic treatment (the internal acoustics of the room). I do. [The two things are also obviously connected, but I don't want to clutter the discussion with this.]

Later.
 

spitzer

New member
What is soundproofing if it is not reducing the sound level to the outside??? The guy in the video I mentioned achieved a reduction in volume measured from the outside (and very clearly heard in the video), thus yes he did SOUNDPROOF a room with curtains. Which particular frequencies were reduced is completely irrelevant, if the VOLUME IS REDUCED, that is soundproofing, period.

Rob: a drop from 65 to 55 dB is HUGE. 55 dB is approaching ambient noise. In fact, outside that exceeds ambient noise. Basically, as it is, I can play drums after midnight and not bother anyone outside.

Someone still seems to be reading the issue flat out wrong. There is NO need for complete isolation (50 dB drop) for that bedroom wall, and anything like that is not going to be done. I can not put it clearer than that.

And Rob... I NEVER said anything about a "cube"! Where did you get that from? Also, "a wooden box" is just misunderstanding.

What I was proposing actually WAS a "second wall" with an air gap, just not the ENTIRE wall. Is that clear enough? PLEASE explain to me why that would not help anything. It adds mass, which by itself should help, and designing it somewhat intelligently what concerns the air gap (CONTAINING ABSORBING MATERIALS) should help even more. It's somewhat like a gobo next to the wall. It's also kind of like an absorber, the reason for that being that an absorber can be designed for particular frequencies.

So let me say that again. A second wall, but covering only part of the wall. What's the matter? What would it do? WHY would it NOT do this or that (take your pick) acoustically.

Oh... and no one's answered this yet. Absorbers absorb sound. Once the sound is absorbed, it is gone. So there is less sound to propagate through ANY wall. So the volume level on the other side is reduced. No one has refuted this, and no one has explained WHY that would be false.

Sorry for being blunt. I felt it was necessary because there seems to be a constant misunderstanding of what's going on.

Respectfully.
 
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