The Drum Bubble - Leaks in my space

[Ekimtoor1]

It’s certainly clever but if it slides horizontally what compresses the join? Surely at some point it must move towards the hole in the wall? I can’t see how this happens. My thinking is that if a heavy door can glide past the opening easily, then the seal thickness and material is the only barrier to sound. I’ve probably just not been able to see how you‘ve sealed this in your mechanism

The rollers press the seals together. But it’s not perfect. The seals are made from strips of mass loaded vinyl which is a good material, but it does not compress and therefore there are small gaps of 1/32” or so in various places across the seal, because the mating surfaces are not perfectly flush.

Still, it does work somewhat as is. I’m going to add some 1/4” neoprene foam tape to one side of the seal. That does compress and it should make a very good seal across those slightly uneven surfaces.

I hope that made some sense.

Mike

 

[jamesperrett]

Air. Hmm. I remember reading about using air but literally no one I talked to recommended it for my project. It was either r13 fiberglass or safe and sound rock wool.

I'd missed the fact that you are using a room within a room so effectively you have an air gap. Yes, you'll probably fill much of the gap with something absorbent to stop the sound bouncing around the gap but it sounds like the air gap is doing its job. With doors I find that 2 reasonably solid doors with a gap between them are better than one extremely heavy door.

 

[Ekimtoor1]

Hey thanks for the comment.

Too late I already built a 300 pound slab ?

 

[rob aylestone]

In truth, I suspect you just did what we’ve all done, and Gervais mentions in his book. Gone overboard by making a door so good it works better than a wall, but then accepting gaps and less effective areas in the joins. Only as good as the weakest link. My studio also has another feature. It’s not wide but long with the entrance at one end. If something happened, I’d be stuck. Last week something fell over which stopped the door, which opens outwards, opening more than a few inches. I had to phone my wife to come home and let me out! If there had been a fire ………………? So at the other end, there is a place where one of the vertical timbers has a saw cut meaning that I could kick through the drywall layers on both sides and have an escape route. It would not be easy, but at that point, possible. One door, loads of equipment left on for ages and loads of wiring. Even worse, if you have ventilation allowing fresh air in, you could also bring in smoke. How many of us have any filtering?

 

[Ekimtoor1]

In truth, I suspect you just did what we’ve all done, and Gervais mentions in his book. Gone overboard by making a door so good it works better than a wall, but then accepting gaps and less effective areas in the joins. Only as good as the weakest link. My studio also has another feature. It’s not wide but long with the entrance at one end. If something happened, I’d be stuck. Last week something fell over which stopped the door, which opens outwards, opening more than a few inches. I had to phone my wife to come home and let me out! If there had been a fire ………………? So at the other end, there is a place where one of the vertical timbers has a saw cut meaning that I could kick through the drywall layers on both sides and have an escape route. It would not be easy, but at that point, possible. One door, loads of equipment left on for ages and loads of wiring. Even worse, if you have ventilation allowing fresh air in, you could also bring in smoke. How many of us have any filtering?

The gaps will not stand! I will furiously fight them to the death! Well, maybe not death but I will prevail.

Being trapped is a real danger and changed my design. Originally, I intended to have a series of clamps on the inside that would pull the door tight into the seal. But if I had a heart attack and went unconscious or something, it would be pretty dramatic to break in from the outside, the room being built as it is. And no one would even know if I was in trouble.

So I went to the design I’m using now which allows someone to easily slide the door open. There are no locks or clamps or other mechanisms preventing entry.

I have some parts coming this weekend that should solve the seal issue.

 

[Slouching Raymond]

Last week something fell over which stopped the door,

Been there, done it Rob.
I have a lockable fire door, on the rear of my living room, which is the only way to the rear of the ground floor (dining room, kitchen, and garage).
It was locked, with the key on the living room side, which is easy enough, but a piece of board fell over on the rear side, and blocked the door from opening.
Couldn't move it, because I coudn't get to it to move it.
I made some L-shaped contraption, to slide under the door, and hopefully the board, then rotate it to lift up the board a bit.
I could then open the door a tiny bit, to get some tool through to nudge the board just a bit.
Lots of bits later, I was able to open the door properly.

Being trapped is a real danger and changed my design.

There is a similar problem with commercial freezer rooms, so they have a big knob you can push from inside to open the door.

 

[Ekimtoor1]

]

 

[Ekimtoor1]

I have finished my “Drum Bubble” aside from a few details.

Recap: it is a 2”x4” framed structure 7’x9’x8’. Ceiling is 16” on center, walls are 24” on center, safe & sound rock wool in the bays.

It is built as a room-in-a-room in my garage on concrete slab with a 2” space between the structure and a concrete block outside wall and a standard 2”x4” inside wall. The garage ceiling is 9’6” high so there is a 18” gap between the roof and the garage ceiling.

Two layers of 5/8” drywall with green glue in between are installed inside and outside, all four walls, ceiling and roof. I had a lot of drywall scraps left over and I piled those on the roof loose, which almost made two more layers.

The door is a sliding affair constructed just like the structure. It weighs about 300 pounds. It took a few tries to get the seal right but it is now tight with no leaks.

I tried a window AC but it leaked like crazy so I took it out, restored the opening and I’m testing another AC device which doesn’t require a big hole in the wall.

So today, I did the first test of the room with my 6.5” Rockville studio monitors. I cued up a bass heavy recording and cranked it up to 100db. Closed the door and took a reading just outside the door at 67db. Not quite the 55 STC I was hoping for, but pretty good!

Outside the house, on the sidewalk - nothing. Outside the adjoining concrete wall, if I put my ear to the wall I could detect a little low end.

Inside the house, in my granddaughters living room which adjoins the bubble, quite a bit of low end bleed, which I expected.

In the other parts of the house, next to nothing.

An acoustic drum set is a much different animal than the 100db music I was playing and I predict there is going to be an extremely low amount of bleed from that, if any. This is the result I was hoping for.

Things I haven’t done yet:
Sealed the outlets and light fixtures
Applied an acoustic sealant around
the bottom plate of the room.
Installed another row of weatherstripping
To the door seal.
Applied absorption panels inside

Being that most of the leakage is low end resonance, I’m not sure those extra measures are going to improve that, but I’ll probably do them anyway.

Cheers!

 

[Slouching Raymond]

Looks like you've cracked it.
I don't even turn on my ventilation. If it gets too warm in there, I just open the door, and go take a break.

 

[rob aylestone]

Before you do anything - work out why your predicted reduction was different. It sounds like you need to now go around with your 100dB inside noise source blasting away, with a microphone and a pair of enclosed headphones and track down where the sound is escaping. Do this before you waste any time increasing the efficiency of the parts that are performing. Listen for the weak areas and fix just those. running a live mic around the outside will let you spot the maybe small leaks. I've often thought a phone and app would be good for this as theyre small enough to sweep around edges, seals, cable punch throughs, ducts etc. I have, with a mic and headphones, found a panel where a drywall screw had gone into a part of the outside structure and that whole panel was letting the sound through. Removing that one over length screw fixed. I found a gap at the top of one wall where the ceiling was sitting just a few mm up on a screw protruding from the top plate - just enough to lift it and compromise the seal. We've done the door seal, I know - but worth seeing what is squeezing through. Any ducts from inside to out are obvious routes to check. You can even get a tiny gap at the floor level where a timber sits on a slightly uneven floor with a small depression. Hard to see but possible. You can also do the smoke inside test to double check for these little compromises.

No point increasing isolation where it's not needed, so it's a quest for weak areas now.

In terms of noise transmission annoyances - a repetitive kick drum even at really low levels can be far more anoying than a bit of everything.

 

[Ekimtoor1]

Looks like you've cracked it.
I don't even turn on my ventilation. If it gets too warm in there, I just open the door, and go take a break.

I would do that but, I’m in south central Florida and even in the winter my garage is 80-90 degrees. In the summer? Forget about it. It often hits 100 and higher.

 

[Ekimtoor1]

Before you do anything - work out why your predicted reduction was different. It sounds like you need to now go around with your 100dB inside noise source blasting away, with a microphone and a pair of enclosed headphones and track down where the sound is escaping. Do this before you waste any time increasing the efficiency of the parts that are performing. Listen for the weak areas and fix just those. running a live mic around the outside will let you spot the maybe small leaks. I've often thought a phone and app would be good for this as theyre small enough to sweep around edges, seals, cable punch throughs, ducts etc. I have, with a mic and headphones, found a panel where a drywall screw had gone into a part of the outside structure and that whole panel was letting the sound through. Removing that one over length screw fixed. I found a gap at the top of one wall where the ceiling was sitting just a few mm up on a screw protruding from the top plate - just enough to lift it and compromise the seal. We've done the door seal, I know - but worth seeing what is squeezing through. Any ducts from inside to out are obvious routes to check. You can even get a tiny gap at the floor level where a timber sits on a slightly uneven floor with a small depression. Hard to see but possible. You can also do the smoke inside test to double check for these little compromises.

No point increasing isolation where it's not needed, so it's a quest for weak areas now.

In terms of noise transmission annoyances - a repetitive kick drum even at really low levels can be far more anoying than a bit of everything.

Thank you for all those excellent suggestions.

Looks like I have misunderstood the STC calculation and I just read that it doesn’t mean much anyway for a real world result. The way I did the test is the most valid, setting up a sound source inside the space and measuring the DB outside the space to get the DB reduction. My first test shows a 33 DB reduction which is decent but for sure I’d like more.

My ears tell me that practically all the leakage is low frequency. I believe that is resonance through the concrete slab, which the entire house is built upon. The exterior walls are concrete block. The bubble has no decoupling material on the floor other than a thin layer of indoor-outdoor carpet. So perhaps that is my first target.

What do you think?
Mike

 

[rob aylestone]

I'd move to the 20-20K sweep test. That's always quite revealing from outside a space - you also discover all the nasty vibrations and resonances. I did this in my summer theatre (for fun and interest really) and with lots of potential volume, the sweep was hugely good at revealing things that vibrate and where they are. The building is a steel framework - clad inside and outside with cement based sheet material and good old asbestos!. No insulation whatsoever - just an air gap. With around 20KW of amp power and a flown array, the result inside was a bit scary with all sorts of things suddenly taking off, but from outside the building - it holds 1400 people seated. Outside it was quite revealing. nothing audible outside till about 30Hz when the noise rose sharply. By 2K the lev el outside was falling off and by 5K, gone! The bass end travelled through the structure easily. The theatre is on a pier, so that's timber, steel and more timber! You might find the leakage is at a very specific frequency, but the baseline for my studio at home was a simple one. Can I work at normal volume at 11pm when it's very quiet. I can just hear a kick drum, just..... The weak link in my studio is the opposite of yours. The door. A simple, ordinary timber house type door. I meant to add a couple of layers, but never got around to it, because it's good enough, and the bass is like you, probably going through the concrete floor!

 

[Ekimtoor1]

I'd move to the 20-20K sweep test. That's always quite revealing from outside a space - you also discover all the nasty vibrations and resonances. I did this in my summer theatre (for fun and interest really) and with lots of potential volume, the sweep was hugely good at revealing things that vibrate and where they are. The building is a steel framework - clad inside and outside with cement based sheet material and good old asbestos!. No insulation whatsoever - just an air gap. With around 20KW of amp power and a flown array, the result inside was a bit scary with all sorts of things suddenly taking off, but from outside the building - it holds 1400 people seated. Outside it was quite revealing. nothing audible outside till about 30Hz when the noise rose sharply. By 2K the lev el outside was falling off and by 5K, gone! The bass end travelled through the structure easily. The theatre is on a pier, so that's timber, steel and more timber! You might find the leakage is at a very specific frequency, but the baseline for my studio at home was a simple one. Can I work at normal volume at 11pm when it's very quiet. I can just hear a kick drum, just..... The weak link in my studio is the opposite of yours. The door. A simple, ordinary timber house type door. I meant to add a couple of layers, but never got around to it, because it's good enough, and the bass is like you, probably going through the concrete floor!

I will definitely do that sweep, although I’m pretty sure all I’m going to find is that low frequency resonance. I used acoustic sealant at every layer and staggered all the drywall seams and then there’s the green glue creating a gasket over the whole structure, so I’m pretty confident about the envelope itself.

My next move is to do the things I was going to do anyway, measuring along the way. Bass traps and diffusers are next.

What would you use to decouple your concrete floor?

Thank you!
Mike

 

[rob aylestone]

Too late really - neoprene between the bottom of the wall bottom plate, but you could add a small height adjustment to the floor - 1" timber on neoprene strips then a floor on top of that. helps impulse noise and mechanical things like kick pedals, and things you actually hit. It's also a barrier layer between sound getting to the floor.

 

[Slouching Raymond]

What would you use to decouple your concrete floor?

My Esmono came with chipboard strips, about 2.5" wide, with neoprene stuck on top, which the steel walls should sit on.
I augmented that by making a second layer of chipboard strips, so that any cables and particularly a thick analogue snake could pass under the walls.
Inside, the concrete floor is covered by a multi-layer arrangement, as recomended by studiospares.com who supplied the Esmono.
Concrete Floor - Thick underlay - Chipboard - Thick underlay - Chipboard - Thick underlay - Thick carpet. Never had a problem.

 

[Ekimtoor1]

Too late really - neoprene between the bottom of the wall bottom plate, but you could add a small height adjustment to the floor - 1" timber on neoprene strips then a floor on top of that. helps impulse noise and mechanical things like kick pedals, and things you actually hit. It's also a barrier layer between sound getting to the floor.

I thought about that when I built it. I read somewhere that the net gain is next to nothing but you can’t believe everything you read.

Believe it or not, I can get under there because it’s not bolted to the floor. It’s freestanding. During the build, I had the unit out 2’ from the walls, otherwise I would never have been able to get the drywall on. After I got the drywall on the two exterior walls and roof, I was able to pry up a corner with a wrecking bar and get a short piece of 1” pipe under the plate. After getting all four in, I was able to roll the whole structure into it’s final spot. First in one direction, then change the pipe to the other direction and repeat. It worked so well I couldn’t believe it!

Even though the unit now weighs twice as much, I’m sure I could get some neoprene in there. I just wonder if it’s worth the trouble.

Thanks!
Mike

 

[Ekimtoor1]

My Esmono came with chipboard strips, about 2.5" wide, with neoprene stuck on top, which the steel walls should sit on.
I augmented that by making a second layer of chipboard strips, so that any cables and particularly a thick analogue snake could pass under the walls.
Inside, the concrete floor is covered by a multi-layer arrangement, as recomended by studiospares.com who supplied the Esmono.
Concrete Floor - Thick underlay - Chipboard - Thick underlay - Chipboard - Thick underlay - Thick carpet. Never had a problem.

A couple questions: is chipboard the same as OSB? What thickness? What is the composition of the underlay? By any chance are there any data about how well that works?

Thanks!
Mike

 

[rob aylestone]

I think our 'chipboard' is your particle board? OSB is those compressed larger flakes of wood. It's structurally more strong. Here we have chipboard that has tongue and grooved ends so they're good for under carpet, wood laminate or vinyls. OSB is not smooth, so that might matter? The only thing I have discovered is that the usual 60cm on centre is not good for studios where there are heavy spot loads. I have some heavy duty loudspeaker stands that stand on spikes, and in my old studio incarnation the spacing between the support timber let the chipboard warp into the gap. We can also get MDF with tongue and groove edges which is nice but the edges can crumble if a join is between two piceces of timber and they rub together as you walk across. Currently I'm working with an extra longitudinal support making 30cm/1ft between them and this works well. The neoprene strip does fill any ups and downs. I'm not certain of the resilience of it, because the walls and ceiling weight is considerable so it compresses quite a lot. The type of stuff I have always used is this.
neoprene

I had some carpets changed at home and the old underlay was rubber and branded dunlop. This went under the MDF floor of my old drum room (it's gone now) and this I think helped quite a bit and wasn't even expensive.

 

[Slouching Raymond]

Rob describes chipboard well. Squashed tiny flakes of wood, unlike MDF, which is moor like paper.
Before I bought the Esmono, I made some tongue and groove chipboard panels, with 3 layers of this underlay attached, to line my dining room, for drumming.
I later recycled it to make the Esmono floor. Had enough left over for another floor in my second Esmono, and I still have more stored away.
Here is the underlay. I think I bought 6 rolls at around £94 each. It is good stuff.

You can see the thickness is 2/10". Also, you see the little bobbles of rubber embedded in the gooey side.

This pic shows the double chipboard strips I mentioned, with the neoprene on the top, which the wall sits on.
Also shows a table leg dangling in front of the open door. Its other three legs rest on the carpet inside the room.
This shows you how thick the multi-layer floor is. That rule is tenths of an inch. The inside layers go all the way down to the bottom of the rule.
I'm not quite sure, but there may even be THREE layers of sandwiched chipboard in the floor, not 2 as I said.