Help With a Drum Room Problem?

I contracted a builder to construct a drum room. It's a roughly 5mx5m room. The outside is block and concrete. Then they sprayed the interior with polyurethane foam (to seal it, as concrete and block generally has small cracks) and built another room inside out of drywall, with about 10cm between the interior and exterior walls. The interior room has four walls and a roof. Given that the floor is solid concrete and is resting on a foundation on top of about 4-5m of refill (my land sloped down towards the back and was refilled) I didn't see a need to do a floating floor. We then finished it with two doors.

And while I'm happy to have it, the problem is, it's a drum dampening room. It is not silent. You can hear muffled drums from outside. And if you stand next to the room and put your hand on the outside wall you can feel the wall vibrating as someone plays (toms, not just the kick).

I think the problem is where the doors are installed. When I presented the original design to the contractor I stressed over and over the need to have the inner and outer rooms entirely independent. The inner door would be mounted to a frame attached to the interior room, the outer door would be mounted to the outer room. There would be a visible gap between the walls in the 'airlock' between the doors. This seems standard for drum rooms.

The contractor, however, insisted that the inner frame would not be strong enough to support a door of sufficient mass to block the sound, so he decided to have the two rooms come together at the door frame. He made a very thick concrete door frame and tapered in the drywall to meet it at the door, kind of like a V. Then he hung both doors on that thick concrete frame.

I brought this design detail up repeatedly both in planning and as the room was being constructed but he just insisted we try it his way and if it didn't work, he would "make it right". Several times I thought of putting my foot down and insisting that he do it my way but I knew that if he did, and at the end the room was unsatisfactory for any reason, he would then have an "out" - he could just say my design was wrong, etc.

So we went with his design.

Well, it didn't work. And now he's over budget and all he wants to do is try little hacks like adding more Sonex panels, maybe putting my drums on an isolation platform, etc. The room is plastered with Sonex. More Sonex will not make the walls stop vibrating.

Thankfully I did not pay the entire contract up front. So I have the whip hand: if he wants to get paid he has to make it work.

I just want to be sure that the door area is the issue. It seems to be the only outlier, and it's the only thing I can think to change: re-do the doors so the rooms stay isolated at that point, and hang a thicker door on the inner frame (he chose an acoustic glass door for the inner, although I insisted on a vault door for the outer).

Certainly fixing that error can't make it worse. But I'd appreciate hearing any thoughts anyone has regarding the matter.
 
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brentcn

Platinum Member
Well, you can find out where the sound is coming from by using a DB meter while someone plays the kit. That's the only way to prove that the door/frame really is the culprit.

And you really should wonder if the escaping noise is enough to bother anyone. If someone is outdoors, then yes they may hear it, but if they're indoors with the windows closed, perhaps they won't.
 

Cmdr. Ross

Silver Member
Quite the project.
As for the door, you could get by with foam panels covering the inside and having a security door with foam pannels attached to the inside of the outer door (picture opening the inner door from the inside & staring at foam panels attached to the security door).
That way it's not only secured, but there are 2 layers of foam the sound would have to get through.
Win-win.
 
Quite the project.
As for the door, you could get by with foam panels covering the inside and having a security door with foam pannels attached to the inside of the outer door (picture opening the inner door from the inside & staring at foam panels attached to the security door).
That way it's not only secured, but there are 2 layers of foam the sound would have to get through.
Win-win.

This was the first thing they suggested. They put Sonex on the inside and outside of the inner door, all around the frame between the doors, and on the inside of the outer door. The difference was negligible, but I think that's largely because of their choice for the inner door. They chose an aluminum frame door with double pane glass, which mystifies me. The architect's whole reason for unifying the doorway was to support a heavy inner door. They would have put the same type of door on the outside except I insisted it be a security door.

The outside door is great, it's basically an iron vault door and it's super heavy. To my ear the sound absorption is the same with and without the inner door closed.

The first thing I suggested, other than separating the frames at the doorway, was to replace the inner door with one like the outer. It would be an additional material cost out of my pocket but I think that's the next logical step. And if that doesn't do it, then I would want to fully separate the rooms.

As far as the noise reduction goes, it's muffled but definitely audible for a fair distance. Winter helps due to closed windows but in Summer, and at night, I imagine it would bother a neighbor. It's certainly a lot better than no muffling at all but I have seen and used better drum rooms.
 

Supergrobi

Technical Supervisor
Staff member
Sounds highly suspicious. A couple of questions: Is there any kind of mineral rock wool between inner and outer walls? Do the inner and outer walls have any kind of contact - even through the floor? Does the floor inside have any contact with the outer walls?
 

Cmdr. Ross

Silver Member
And you really should wonder if the escaping noise is enough to bother anyone. If someone is outdoors, then yes they may hear it, but if they're indoors with the windows closed, perhaps they won't.

Then this is my next thought. If you've already gone to such legths to isolate the noise, then what comes out now is a blessing to those around the building.
Have fun and don't worry about them.
 
Sounds highly suspicious. A couple of questions: Is there any kind of mineral rock wool between inner and outer walls? Do the inner and outer walls have any kind of contact - even through the floor? Does the floor inside have any contact with the outer walls?

The space between the inner and outer walls (and inner and outer ceiling) is open, about 8cm (it was 10cm but they applied about 1-2cm of polyurethane foam over the interior of the outer shell).

The floor is continuous: it passes under and makes contact with both walls. This was necessary both for cost and because the builders didn't know how to do it any other way (it's a gigantic heavy concrete slab on top of compacted dirt). My first drum teacher had a room in suburban California to the same specs and a little kick vibration leaked, so I knew it would be a compromise. But I really doubt this is the prime contributor to the amount of leakage we're experiencing.
 

Supergrobi

Technical Supervisor
Staff member
Nothing is stopping the floor from transfering the vibrations from the inside directly into the external walls. The inner walls don't have that much effect because there's not enough transition of vibrations between air-borne and body-borne and nothing generating any friction for the moving air, e.g. through some mineral wool. Also there's no dampening of the vibrations of the inner walls through mineral wool, they're resonating like a huge drum shell. The doors aren't that much of a problem since two average room doors are enough to reduce noise by a very high amount. The bigger problem is the concrete junction between the inner and the outer frame, which again transfers the vibrations hitting the inner door/walls directly into the outer ones. I'd call this project a misconstruction. Foam assembled onto the inner walls will be of no help at all other than reducing the reflections inside.
 
Nothing is stopping the floor from transfering the vibrations from the inside directly into the external walls. The inner walls don't have that much effect because there's not enough transition of vibrations between air-borne and body-borne and nothing generating any friction for the moving air, e.g. through some mineral wool. Also there's no dampening of the vibrations of the inner walls through mineral wool, they're resonating like a huge drum shell. The doors aren't that much of a problem since two average room doors are enough to reduce noise by a very high amount.

I don't know. A floating floor would have been great. It just wasn't in the cards, financially or in terms of available skill level. And I don't know how much it would have affected things. If you're building a drum room in a condo or a house, vibration transferring through the floor is a concern. For an isolated concrete construction on a slab floor at the back of my property, I don't know how much it would have helped.

I even tested it with a vibrometer. A vibrometer placed on the floor just outside my drum room, on the shared concrete slab, registers 0 MMI both before and during very hard drum playing. Placed on the floor in the drum room itself, right in front of the kick, it registers ~2 MMI with hard playing. So yeah the floor vibrates when I play, but it doesn't appear to travel very far.

And I don't know that mineral wool in the gap is better than air. I'm not sound scientist but I have seen tons of articles, DIY projects, and even played in studios built around the air-gap principle. They seem fine.

The bigger problem is the concrete junction between the inner and the outer frame, which again transfers the vibrations hitting the inner door/walls directly into the outer ones. I'd call this project a misconstruction. Foam assembled onto the inner walls will be of no help at all other than reducing the reflections inside.

Here is where we agree, and that's probably a good thing because it's really the only part of the room I can feasibly alter.
 

brentcn

Platinum Member
I really hate to suggest it now, since the construction is finished, but if you had enough space on your property, I wonder if you could have built a room *outside* of the room, with a separate concrete footing, walls, door, and roof, and if you would have spent more or less the same.
 

jeffwj

Platinum Member
Just curious, where is the ventilation?

Also, can you add mass to the door in the form of mass-loaded vinyl (see link below for one type). Was mass-loaded vinyl added to the inner construction? It is very common to add mass to the wall construction. Maybe your contractor decided against it since you already had the mass from the block/concrete outer wall.

I Googled Sonex, which seems to be a sound treatment product - not a soundproofing product (maybe Sonex makes soundproofing too?) Sound treatment will help the echo inside the room, while soundproofing will reduce the sound transferred to the outside. The Sonex sound treatment will make the room less harsh sounding.


Hope this helps,

Jeff
 
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Push pull stroke

Platinum Member
I’d do a platform for the drum set suspended on tennis balls, before you go doing any other changes. It sounds like the kick drum might be coupling acoustically with the floor, and the kick is the main problem, it’s those low frequencies that really travel. Only a floor tom might also have similar penetration and carry.
 

Blisco

Senior Member
Just curious, where is the ventilation?

Also, can you add mass to the door in the form of mass-loaded vinyl (see link below for one type). Was mass-loaded vinyl added to the inner construction? It is very common to add mass to the wall construction. Maybe your contractor decided against it since you already had the mass from the block/concrete outer wall.

I Googled Sonex, which seems to be a sound treatment product - not a soundproofing product (maybe Sonex makes soundproofing too?) Sound treatment will help the echo inside the room, while soundproofing will reduce the sound transferred to the outside. The Sonex sound treatment will make the room less harsh sounding.


Hope this helps,

Jeff

This stuff really works. I did a 20X15 room in this and I could play drums at midnight with wifey sleeping above without issue.
 
I’d do a platform for the drum set suspended on tennis balls, before you go doing any other changes. It sounds like the kick drum might be coupling acoustically with the floor, and the kick is the main problem, it’s those low frequencies that really travel. Only a floor tom might also have similar penetration and carry.

We're going to try putting a riser, as every little bit helps. But outside the room you can hear it when I hit one of the rack toms. There's significant muffling but if you're near the room it is audible. The tom is mounted on the kick and could technically be transferring into the floor, but the doors still seem the most obvious culprit.

I'm perfectly willing to be wrong. But I watched every step of the construction and it was made exactly how every other drum room I've seen was made - room within a room, space between the walls and ceiling, double door. I have the advantage of a stone and concrete exterior room. The walls are all non-parallel and even the corners have been canceled with placement of angled sheet rock. There's a lot of Sonex to stop any echo.

The only differences are that the contractor used a single, wide doorframe to hang both doors rather than separating them, putting the inner and outer rooms in contact; and he used a pretty light interior door. So if the platform doesn't make much of a difference those are the only things I can think to try changing.

If I do convince the contractor (or another contractor) to break the single door frame in two, what should the interior frame be made of to support a door as heavy as the outer concrete shell?
 

Push pull stroke

Platinum Member
We're going to try putting a riser, as every little bit helps. But outside the room you can hear it when I hit one of the rack toms. There's significant muffling but if you're near the room it is audible. The tom is mounted on the kick and could technically be transferring into the floor, but the doors still seem the most obvious culprit.

I'm perfectly willing to be wrong. But I watched every step of the construction and it was made exactly how every other drum room I've seen was made - room within a room, space between the walls and ceiling, double door. I have the advantage of a stone and concrete exterior room. The walls are all non-parallel and even the corners have been canceled with placement of angled sheet rock. There's a lot of Sonex to stop any echo.

The only differences are that the contractor used a single, wide doorframe to hang both doors rather than separating them, putting the inner and outer rooms in contact; and he used a pretty light interior door. So if the platform doesn't make much of a difference those are the only things I can think to try changing.

If I do convince the contractor (or another contractor) to break the single door frame in two, what should the interior frame be made of to support a door as heavy as the outer concrete shell?

I’d make sure that riser is on tennis balls, with only the balls touching the floor. And you might consider hanging a couple of heavy moving blankets over that door on the inside. That might be a simpler option. I really doubt the amount of sound coming out, with a tennis-ball riser and blankets over the door, will be noticeable to any neighbors at all.
 

Supergrobi

Technical Supervisor
Staff member
Maybe I've been a bit offhanded in my last post, if so, I'm sorry for it.

There's a couple of physical realities you're facing when dealing with sound in this way. A drummer forum is highly likely a place where this topic pops up on a regular base so I'm feeling like putting together a tutorial/FAQ/best practice sheet to not repeat oneself over and over again might be a good idea, but that's future talk. At the moment we're dealing with huge water inflow in our acoustically optimized facility ourselves so not that much time left for anything else. But maybe I should start putting together a couple of thoughts and facts in this thread. So please see this as a more general approach trying to shed some light onto this topic, rather than a step-by-step advise for your specific problem.

I'm sorry but I have to stand by my claim that nearly everything you built didn't have that much effect on your sonic insulation, maybe even contradicts your efforts.

It doesn't have to cost a cow to do it properly but one has to follow the rules to make a success.

#0 General concept

What we're trying to achieve is to turn comparably fast vibrations of air and material inside the ears range (which can be physically translated to energy) into heat before it hits a bystanders ear. This can be achieved in various ways, depending on the source of the sound (e.g. a guitar amp can be easily detached from floor and walls, for drums or a piano it's much harder), the layout of the room (e.g. huge windows will make things highly expensive and small rooms don't leave enough space for insulating installations), the structure of the rooms floor/walls/ceiling and all the adjacent structures (any concrete floors, pipes or wooden timbers leading into the room from the outside?) connected to the outer world.

It's highly important to investigate the problem you're working against first to not throw a pile of spaghetti onto a wall and see what sticks.

In the case of drums it means to get a feeling for the kind of noise to be reduced. Is it more like a specific tone from a single tom which is carried over the most? This could mean that a thin wall is starting to resonate at the same frequency, carrying the sound into the buildings structure. Some sort of dampening put onto this wall could reduce the noise enough to reach your goals. Is it more the attack of the hit itself like e-drums produce (much more than acoustical drums) then maybe just putting the set onto a floating panel could help in that case. Play around with the source of sound and have someone else hear/measure what's going on in the spot meant to be quietened. Maybe taking a tom from its stand while hitting it to distinguish between the different ways the sound travels through the air/structure. Which leads us to the next chapter:

#1 Air-Borne vs. Structure-Borne

For a better general understanding it's important to distinguish between air-borne and structure-borne sound. Air-borne sound declines quite fast, doubling the distance reduces the sound level by a half, which means 6dB. Compared to structure-borne this is a comparably fast decline, since, depending on the material, structure-borne sound can travel even miles without a hassle.

If you stimulate a hard structure which is attached to another hard structure (e.g. a wall which is attached to a floor) the sound travels directly into the adjacent structure and gets carried over to the next structure and the next... This is how people on the 10th floor still hear the drummer practicing in the basement - the sound travels directly through the walls, standing on each other, up to the roof. Even a pipe can make your sound travel into the neighbors building, or a wooden timber, once activated, sends it over to another room.

The same is true with air-borne sound. If you don't stop the air from transporting the sound waves they'll travel very far. This in fact means that a wall missing 1% of its surface area is considered as non-existent acoustical-insulation-wise.

The absolutely best method in absorbing sound waves is making them transition between structure-borne and air-borne as much as can since this passage eats up the most energy.

Anecdote: while building the Klangwerk (a bunch of studio and rehearsal rooms I'll come back to later on) my friend was standing in the next room, removing some screws from the ceiling. The walls were already built, doors open, so we had to yell very hard to understand each other. I was doing some measurements for the air conditioning. And suddenly something metallic fell to the floor in my room. I could hear it absolutely clearly. And then another piece, and another one. So I was getting nervous because it sounded like directly behind me. Turned out it was the concrete floor, carrying the sound the falling screws made, directly into this highly insulated room. One couldn't tell any difference between their sound in the other room and the one I was hearing.

Conclusion: we lent a huge buzzsaw to cut the concrete between all the rooms - in the middle between the walls - to stop the sound from traveling between the rooms, which worked perfectly well. No falling screws anymore. You'll see it in the video at around 3:39.

#2 Mass

This is one of the more important concepts for acoustical insulation - the mass a structure-borne sound is supposed to pass for insulation should be huge. Everything else works contrary. This means a stone wall is very good for this, even concrete can do a good job. Although a wall made from single stones is the much better choice since all stones are kind of structures on their own while the cement between them helps in stopping the structure-borne sound while traveling. Compared to a concrete wall - a single structure, transporting vibrations without any hindrance. If you build a room in a room one should prefer at least simple dry walls, better choice would be fiber reinforced panels - and even do it double-ply at best. The material doesn't like to resonate and is very heavy.

In your case you've set up thin, non-dampened walls (even made from wood?) which act like a huge resonance chamber, like a guitars body, a drum shell or a pianos baffle. So they start vibrating, resonating (amplifying) at frequencies depending on the material, size and thickness, maximizing your problems. I guess they are attached to the floor and the inner ceiling directly (a couple of average screws are enough) which makes the vibrations travel into the adjacent structures without any hindrance.

For a floor it's the same - a concrete slab carries vibrations very far (as stated above), soil eats them up nearly completely.


#3 Dampening

There's a reason for the selection of images googling "acoustical insulation". And even the wikipedia article states that this is the most important way of insulating. It has various effects. One of the more important is dampening the adjacent walls to reduce their motivation to vibrate, like a moon gel or a towel/pillow attached to bass drum heads is doing. This way you reduce resonating of mass. Another effect is a constant travel between air-borne and structure-borne sound within the material itself. It also hinders the air particles to flow freely. And it brings even more mass to the game. If the construction keeps a distance between the wool and the dry wall, it might be a good idea to help with some styrofoam, directly attached to the panels, to reduce the resonance (you'll see it in the video at ~2:40).

Dampening in order to reduce reflections inside the room also helps a bit, but that's not that much in comparison with all the other concepts.

#4 Delinking

One of the more important concepts. It's all about separating structures from each other to hinder structure-borne sound to travel between them. If a sound wave hits a wall which is directly attached to the ceiling, it sends the sound waves it receives directly into the ceiling, which then adds up to even more noise in the room above. If a room-in-room is built, directly mounted to the walls/floor/ceiling of the outer room, it doesn't make too much sense since it sends all the vibrations received directly into the outer walls, too. If the inner rooms walls/ceilings/floors are connected to each other it also adds up to a resonant sound chamber. This means one has to de-link everything as much as possible.

#5 Room-In-Room

E.g. building a wall for a room-in-room construction, it should stand on something insulating, maybe a rubber strip or something like a thick carpet or the like to separate it from the floor. Use the least possible amount of screws to attach it to the building. It's better to hang the ceiling first,( using acoustically optimized joints at best) and then to construct the walls underneath it, standing on rubber. The wall should also be delinked from the ceiling by using some soft material between both of them. Attaching the panels to the walls construction should also happen in a delinking manner - put some strips of carpet onto the construction first and then screw the panels onto it. All of this doesn't have to cost a lot, it's just that following the concepts with whatever solution gives the best results.

#6 Doors

A single door doesn't help that much. Normally doors are hovering over the ground, leaving a small gap between the doorstep and the leaf. You should avoid this gap at all costs. Having a 2cm gap under a door of 2m height the door can be considered as non-existent sound-insulation-wise. Doors should have a rubber seal around them (or the frame) to not let any air flow between the inside and the outer world. Adding a second door, the frames of both doors shouldn't have any kind of contact (floor, lintel, doorstep) between them. If one of the doors is an acoustically treated one (heavy!) it's even better, but normally two average room doors will do a tremendous job for you.

#7 Windows

At least in Germany there's more or less sound-proof windows all over the place, mainly in order to reduce energy costs. Nice side effect is a quite good acoustical insulation. But there's even special, acoustically optimized windows available. For insulating a sound booth a single window is not enough, unfortunately. The cheap solution is to build panels with insulating material attached, being put into the windows openings while rehearsing (to be able to let in some fresh air if needed), the way more expensive - but highly effective - version is to add a second window, a bit smaller/larger that the original one to let them open inside each other. The glass should be made at least from two plies, better three. Also there's acoustically treated window frames available. Very expensive, should only be applied if that's the real problem. Otherwise it's just throwing money down the drains.

Klangwerk

As said, currently me and a friend of mine are building a 400m² facility of studios and rehearsal rooms inside a 500yr old barn made of 1m thick stone walls. This is the fourth pro-grade studio I built in my life so there's at least a little knowledge about this topic. We already achieved a nearly full acoustical insulation between two rooms located directly next to each other, since the goal was to have a grind core band rehearsing in one room while having a bunch of pupils doing recorder lessons in the next one.

Mission accomplished.

Currently I'm cutting a video showing the making-of-Klangwerk, which is in the making still. It can be considered around 20% done. I've uploaded a first version to youtube so you can have a glance into what we were doing for the last 20 months or so. I don't say one has to do it like this to achieve his goals but it gives a good impression of how to put all those concepts from above above into place.

 
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brentcn

Platinum Member
We're going to try putting a riser, as every little bit helps. But outside the room you can hear it when I hit one of the rack toms. There's significant muffling but if you're near the room it is audible. The tom is mounted on the kick and could technically be transferring into the floor, but the doors still seem the most obvious culprit.

I'm perfectly willing to be wrong. But I watched every step of the construction and it was made exactly how every other drum room I've seen was made - room within a room, space between the walls and ceiling, double door. I have the advantage of a stone and concrete exterior room. The walls are all non-parallel and even the corners have been canceled with placement of angled sheet rock. There's a lot of Sonex to stop any echo.

The only differences are that the contractor used a single, wide doorframe to hang both doors rather than separating them, putting the inner and outer rooms in contact; and he used a pretty light interior door. So if the platform doesn't make much of a difference those are the only things I can think to try changing.

If I do convince the contractor (or another contractor) to break the single door frame in two, what should the interior frame be made of to support a door as heavy as the outer concrete shell?

The mass of the door doesn’t matter as much as having a good seal all the way around, on both doors. Decoupling them further increases isolation. An “exterior” door should be fine; no crazy framework required. But you’ll have small gaps around the edges that you’ll want to address.

What’s the ventilation like? I’d try to have the HVAC system on a wall that faces away from the neighbors since some noise is certain to escape.
 
Maybe I've been a bit offhanded in my last post, if so, I'm sorry for it.

Perhaps not offhanded, but it doesn't seem to indicate that you read what I posted.

The walls of my room do not touch the exterior ceiling. The interior room has its own ceiling, about 10cm below the exterior ceiling. It is a true room within a room, with the exception of no floating floor and the design change made by the contractor which I indicated: at the door frame the interior room comes into contact with the outer shell.

A floating floor is just not going to happen. I can build a platform for the drums, but I really don't think floor vibration is the main culprit here. It's on a gigantic concrete slab at the back of my property that doesn't contact anything else. The human body is an imperfect vibration conduit. But I can hold a tom in my hand, strike it, and sound transfers. Given that the only differences between my room and a "perfect" room are the lack of a floating floor and the point of contact at the door frame, I strongly suspect the door frame is the issue.

Again, I'm willing to be wrong. But when someone just dismisses the whole construction it is a bit hard to derive constructive criticism from the reply. It's not a "botched construction". For the most part it follows established rules. And, largely, it works. From 100 feet away you don't hear the drums. I just think it could be better and I'm looking for ways to improve it.
 
The mass of the door doesn’t matter as much as having a good seal all the way around, on both doors. Decoupling them further increases isolation. An “exterior” door should be fine; no crazy framework required. But you’ll have small gaps around the edges that you’ll want to address.

What’s the ventilation like? I’d try to have the HVAC system on a wall that faces away from the neighbors since some noise is certain to escape.

The ventilation is a mini split AC. The interior portion of the AC is mounted to the drywall. The drain and vent tubes are very small and run to a small offset gap in the wall.
 
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