John Sayers' Recording Studio Design Forum

Please note - I started 4 separate threads at the outset of this adventure.
This one - which has become the main ongoing discussion....

And then,
viewtopic.php?f=2&t=17302 - Should I use (denser) 13ml soundchek or 16mm fyrcheck?
viewtopic.php?f=2&t=17296 - Triple leaf
viewtopic.php?f=2&t=17294 - Please help with options for room within room -

Hi again.
My question is now more simple - would the floor of the level above (where I want my rehearsal room) - which is a hardwood floor nailed/glued to tongue-groove chipboard flooring count as a 'leaf' - when
a) it is so heavy
b) it is 10" away from the draywall leaf below it (the current ceiling downstairs)
c) the airspace between the ceilling drywall and this wooden floor is broken up by the joists and cross-pieces.

Thank you

Peter

Hi Pete,

The simple explanation of what a leaf is is this. It is one heavy piece of mass. Now that can be attached to framing or it could be a free standing block wall...it could be horizontal as in an overhead ceiling or floor system or it could be vertical as in an exterior/interior wall.

The determination comes in many answers as to what is a leaf.

In the strictest of sense, a leaf is determined by the enclosed air around it. In other words, If you have a heavy mass that you are thinking it is a leaf...but it is without sides, no hard boundaries to contain the air...guess what...still a leaf Sorry about eveyone's luck that thinks otherwise:)

The mass of the leaf is almost as much at fault as the enclosed air. Once the frequencies, or rather if the frequencies make it thru the one boundary...and then hit this other hard boundary that has no enclosed air space...the mass still moves the vibrations and dilutes the isolation...in the strictest sense.

Your floor is mass. And the 10 inch air space is good. The biggest issue is that you HAVE to decouple a two leaf system, or any attempt at mass/spring/mass to get the absolute highest degree of isolation available to you from your efforts.


The framing is basically a coupling of the floor...your walls are constructed the same way. The coupling of this type of construction, while required to keep the shear of the structure as high as possible, is not aimed at acoustics in the strictest sense of the word.

You have to look into several things. One is to decouple the ceiling with clips and hat track...and the other...the MAIN thing you should do, is to get your build on the ground...out of an upper floor area...it is just consumed with issues that cannot be overcome by talking about it on a forum, although some might have you believe otherwise.

_________________
Brien Holcombe
_____________________________________________
Sound: You can't stop it, you can only try to contain it.

Thank you so much for the clarity in your reply.
I can see what I need to do now. (Though any other comments would be greatly appreciated!)

Take off all the plasterboard that was used to create this room as it creates 2 leaves on 3 sides and the roof....and is coupled...so will never be great at reducing sound levels out of the room.

This will leave me with
wall 1 - brick (outside of house)
wall 2 - wooden frame with plasterboard on far side (another room)
wall 3 - like wall 2
wall 4 - concrete retaining wall (in fact I might leave this plasterboard sheet in place as it is attached direct to the retaining wall with no battens/air gaps - so is still a single leaf

Plus ceiling - joists with wood floor above

And then build a freestanding wooden frame inside the space (and plasterboard one side - the inside - of this frame - walls and ceiling)
This wooden frame will ONLY connect with the walls mentioned above via the floor. (Which is a concrete slab under the whole house)

Unless someone tells me otherwise - in which case, if you think it's better, I could leave a gap in the flooring I am using (a polystyrene underlay, under a regular timber floating floor) so that the flooring ends at the perimiter of the outer walls...and restarts at the perimeter of the inner walls.

I guess I might as well use all the plasterboard I am taking off to add mass to the existing single leaves left behind?

And I assume I am right that the gap between the INNER and OUTER rooms should be an AIR gap, not filled with insulating wool?

Thanks again for all your help! Green Glue at the ready!

General questions,
How thick is the plasterboard used?
How thick is the concrete wall? Any idea of the type of concrete?


This may constitute a single leaf, however the plaster may not be adding anything in terms of mass, any may in fact degrade the isolating properties of the concrete wall alone - but I'll leave that for someone more knowlegeable to answer.


Depending on it's thickness, perhaps, perhaps not - if it's less than 15/16mm it's not much use.


No, that assumption would be wrong. Light insulation in the airgap has the beneficial effect of increasing the apparent gap from an acoustic perpective.

_________________
Brian
As you slide down the bannister of life, may the splinters never point the wrong way...

The general recommendation here is to use 16mm drywall. Thinner is less effective.

10 mm is way too thin. Even 13mm is "iffy". It's not just adding mass that matters: there are other factors involved too, such as rigidity, flexibility, resonant frequency, etc. Using several thin panels is not a good idea, as the panels still act individually, as well as collectively. Just go with thick layers.

The insulation does not connect the inner leaf and outer leaf mechanically. It isn't solid, and isn't very massive. It only creates a flanking path if you jam it in, compressing it a bit. If you just lay it in, with no compression, then there won't be any flanking. In fact, filling the air gap with insulation does not eliminate the air gap. The air gap is still there. Insulation is mostly air anyway. And as Brian pointed out, adding insulation increase the effective mean path that sound waves must travel, by roughly 140%, so the air gap actually appears BIGGER to the sound waves. Not intuitive!

If you compare two identical MSM walls, one with insulation and one without, the one without insulation will perform between about 5 and 16 db WORSE for isolation, than the one with insulation: That's huge! You definitely need it.

- Stuart -

_________________
I want this studio to amaze people. "That'll do" doesn't amaze people.

Thanks Stuart - clear as a bell. I will fill the space with insulation.

May I ask one final question as there seem to be some different POVs on this.

The floor on which I am building the room within the room is a concrete slab (holding the house upright on the hill!).....

The existing framing (walls 1,2,3) and the brick outerwall all physically touch this concrete slab.

When I build my room within the room - do I put my inner-room framing straight onto the slab....or use rubber strips to separate the framing from the concrete?

Thanks so much.

Peter

My standard answer applies here too: "It depends."!

It depends on your reasoning. If you just want to use the rubber (usually neoprene) to seal the gap under the frame, due your concrete being very uneven, for example, then that will work. But if you plan to use it to try to decouple the frame from the slab, well, that won't be very effective. It won't decouple very well, since you still have to attach the frame to the concrete with bolts or nails! And the bolts or nails create direct flanking paths right through the rubber, mechanically linking the two. If it were possible to just let the wall rest on the rubber, with no bolts / nails, then that could work to "float" your wall, but of course you can't do that in reality, as the wall has to be firmly attached to the floor. However, it IS possible to float walls, floors and even entire rooms, but the cost and complexity are both very high.

- Stuart -

_________________
I want this studio to amaze people. "That'll do" doesn't amaze people.

Hi Stuart and thank you again!

I was actually not planning on using nails to attach the inner room to the concrete slab - but instead - was planning on using a glue that's for sale over here in OZ which is supposed to be good for the purpose.
So I could glue the frame to the rubber and the rubber to the concrete....if the consensus is that this will help reduce sound escaping....

I'm assuming too that my rubber strips have to be wide enough to ensure that (if I'm going down this route) my drywall sheets on the inner room don't touch the concrete either!

All the best
P

Glue? For attaching the wall to the floor? Personally, I would never do that, and the building code where I live absolutely does not permit that.

It's not about sound escaping: it's about floating your wall, which is different. Like I said: there are two reasons you might want to put rubber under the wall. 1) Seal the gap airtight. 2) Float the entire wall (to fully decouple it from the floor). You seem to be talking about #2 here, which is NOT about stopping sound from getting out: it is about decoupling and isolating the wall, to prevent flanking between wall and floor. That's not the same at all.

No, the rubber needs to be the correct width to give you the correct calculated deflection of the correct type of rubber under the real load conditions of the wall, for each section of each wall!

A rubber strip under the floor is great for sealing where there is major unevenness in the floor slab, but that's not what you are talking about, it seems. Rubber can also be used to float a wall, but like I said before, that is NOT easy to do correctly. You need to calculate the total weight (mass) of the wall and of everything that will be attached to it, such as doors, windows, the ceiling, HVAC, electrical, lighting, treatment, decorations, etc. You need to know all of that in advance, because you MUST have the entire total weight correct in order to know what kind of rubber you need, and how wide to cut it. The rubber MUST be compressed to the exact correct working range when the room is finished. If you calculate wrong (or don't bother calculating at all) then there are two possibilities: A) The rubber will not be compressed enough, the wall will not float, and it will be nothing but a very expensive flanking path around the entire room: You will have wasted a lot of time and money for zero effect. B) The rubber will be over-compressed, the wall will not float, and it will be nothing but a very expensive flanking path around the entire room: You will have wasted a lot of time and money for zero effect.

Your chances of everything working out by pure chance or sheer luck are practically nil. For most types of rubber, it must be compressed sufficiently to deflect around 10% to 20% under full load (depends on the type of rubber) in order to float and isolate the wall. Any more or less and it does not work. So you need to know the exact load (kg/cm2) on the sole plates, and use the right type / thickness / width of rubber to get the right deflection. The trouble is, the weight is not constant around the wall: Some places will have higher weight (EG, under windows, under door frames, etc.) and some will have lower (EG. long stretch of blank wall with minimal treatment. So you need to calculate the correct loading for each PART of each wall, and use the right type/dimensions of rubber for each section.

Like I said, that isn't easy to get right. If you are up to the challenge, then go for it! But you also then need to spend much more money to get it right, as you then need to isolate your wall anchors...

Floating works great when done right, but "done right" is not easy...

However, in none of your multiple threads do see the most basic information that you need in order to decide on things like floating walls, air gaps, mass and such like: I don't see your numbers! I don't see how loud you are, how quite you need to be, your TL goal, your MSM tuning frequency, or any of the other basic data that is essential for determining the details of how to build. Maybe I missed that, and if so then please point me at it, but if not then I'd suggest that, before you start chasing after construction techniques that might or might not be useful/doable, you should first get those numbers in place, and define your goals for this build. If you have no goals, then it is guaranteed that you will fail to meet them! If you DO have goals, then you can have a plan, and the chances are much better that you will meet the goals.


- Stuart -

_________________
I want this studio to amaze people. "That'll do" doesn't amaze people.

Stuart - once again a HUGE thank you for taking your valuable time helping me.
My primary goal is to create a space in my house where I can play my trombone without disturbing the baby or the neighbours - please see attached picture.
range - 82 Hz to 520 Hz
volume 85 - 114dB
The room I have selected is on the ground floor on the concrete slab.
The house is 2.5 levels. Level 1 (where the music room is). Level 2 directly above it (our living spaces) and Level 2.5 is offset - like a mezanine from level 2 - as the house is on a steep slope.
The ground floor has a 1.5 m high retaining wall along the side of the hill and then an air gap under the rest of the house.
So the easiest way for sound to travel from the music room, to the baby's room, is over the top of the retaining wall...under the house....and in through the floor of the baby's room.
The original attempt at soundproofing this music room - done simply by using 2 layers of 13ml plasterboard was pretty effective in keeping noise levels to an acceptable level in the baby's room.
However - the noise transference up to the living spaces was unacceptable.
And, the noise transference through the one external wall of the music room to the nieghbour's childrens' rooms was also a bit high.
I am looking for a 50-60% reduction in noise through to our living rooms.
And a 20%-30% reduction in noise to the neighbours
And a 15-20% reduction on noise to the baby's room.

The music room as it stands is 2.3m x 1.9m x 2.6m (high)

My room within the room is probably going to be around 2.1m x 1.7m x 2.4 (high)

Peter

Great! So we have some numbers.

That's the fundamental frequencies, not considering harmonics, but that's good enough as we are only interested in the lowest note. So if the lowest tone you need to isolate is 82 Hz, general rule of thumbs says your wall should be tuned below 41 Hz. Call it 40 Hz.

Once again, that's a theoretical range, but once again, it's good enough for your purposes, since it is the maximum level that counts: Call it 115 dB.

So you've answered the question "how loud are you?" and "what frequencies do you need to isolate?". Now we need to nail down "how quiet do you need to be?".

Unfortunately, percentages aren't much use in acoustics, since sound is perceived logarithmically, and percentages are linear. A subjective reduction of 15-20% is less than 1 dB, and not even audible. Barely even measurable. A subjective reduction of 50% is roughly 10 dB: hardly worth doing! That would still leave the levels outside your room at 105 dB, which is way loud.

There are two ways to move forward here and define the level that you need to hit. For the neighbors, it is easy: call your local municipality and ask for a copy of the noise regulations governing your neighborhood. That will define the legal limit that you must comply with. Regulations usually state that the level must be measured at the property line, so that's what you'll need to do. Get a sound level meter, and get someone to measure, at the property line, the actual level or your very best efforts to blow the roof off with your trombone. Measure during a quite time of day, such as late at night when there are no other loud noises going on in the neighborhood that could skew the reading (traffic, lawnmowers, radios, TVs, etc.). Measure both the ambient level (with no trombone) and the peak level during your playing. Now do the same for the baby's room, living room, and other locations around the house.

This will give you objective numbers, regarding the amount of isolation that you need, and the amount that you already have.

You also mention different levels of isolation in different directions, but isolation is an "all or nothing" proposition. You'll get roughly the same in all directions, especially with low frequencies, since low frequency sound is not directional: once it is out, then it is out and will wrap around objects whose dimensions are smaller than the wavelength. So all sides of the room need to be done to the same level. It is no use designing one wall for 50 dB of isolation and another for 30 dB. If you do that, you get 30dB all around. So EVERYTHING must be designed for the same level: walls, ceiling, doors, window, HVAC and electrical.

You probably don't need to lose that much height. It should be doable with 2.45, maybe even a bit less if your existing joist layout permits interleaving.

However, you'll lose a bit more on the length and width, since you have to allow for the depth of the left wall PLUS the depth of the right wall, (ditto front and back).

So I'd guess at final room dimensions (not considering acoustic treatment: just isolation) of around 2.0m x 1.6m x 2.45m.

Your plan to strip the room down to bare studs / concrete, then beef up the walls and ceiling is good! That's the way to go. Once you have it down to that, post some photos so we can get a better idea of what you are dealing with. If it isn't already sealed, then start by sealing the surface of that concrete retaining wall: concrete is porous, and needs to be sealed. Also, seal all joints and gaps in the other walls around the room, and in the floor above you. That outer leaf must be totally airtight. Even tiny gaps will seriously compromise your isolation. If you even vaguely suspect that what you are looking at might be a crack, seal it. And even if you are absolutely certain that it isn't a crack, then seal it anyway, just in case!

One thing I didn't see in your plan, is HVAC: That room will be sealed totally airtight, twice over, so you won't be able to stay alive in there for very long if you don't have HVAC! You need both fresh air and cooling. Fresh air to stay alive, and cooling to stay comfortable. You can't play your trombone well if you are too hot, and breathing stuffy, stale air. And it's even harder to play if you are dead from suffocation! So you need to consider how to get air in and out, through silencers (to retain the isolation), and you need to consider how to keep the room cool. If your current house HVAC system has the capacity, you can just hook into that. If not, you can do a separate vent system for bringing fresh air in and exhausting stale air, plus maybe a small mini-split air conditioner to keep it cool and dehumidified.

But overall, it sounds like you have a good plan!


- Stuart -

_________________
I want this studio to amaze people. "That'll do" doesn't amaze people.

Thanks again Stuart - all excellent and encouraging!

I'll post photos when it's stripped....and put a link to the dead vent I found that looks achievable...

I do have a ducted heating system which has a fan setting that could force air into the room...but by connecting into this I am connecting the music room to every other room in the house..which makes me nervous. I think (presme??) it would be safer to have a dead vent between the music room and the adjacent (rarely used) room on the ground floor - so if there is any sound leakage via the vent it will be to a space further away from the children's bedrooms/neighbours....understanding what you said about having to think of insulating in EVERY direction! I must confess I am still puzzled about how an air vent can be 'dead' but I'll read more before I post!! There are lots of good examples on this site I know.

Just on those percentages - sorry if I wasn't clear...the numbers I gave relate to the INCREASE in isolation I would like relative to how things are now...(and I'll stop using percentages!!)

Overall I want to get the noise in the children's bedrooms and in the neighbours' bedrooms to be no more than an adult whisper - 30 db...that's 85db reduction from 115db....

I will try and get a proper reading on what things are now - but my wife says that the noise in the baby's bedroom was half way between talking and a whisper - so say 50db??

So my hope is that by doing a proper soundproof room rather than just the current double plasterboard setup, I will get an improvement from 50db in the bedroom to 30db or less. (i.e. an improvement in db-reduction from -65db to -85db)

In terms of the livingrooms - my wife says it sounds like the trombone is in the room - so if I can get a reduction down to something less than normal talking - say 40-50db (i.e. -65 to -75db) that would be great! Of course, if I can get it down to whisper quiet I will!

NB re your comment on tuning the wall below 40 Hz....I'll read some more about what this means in terms design etc!

Thanks again - your help is FAB!

Peter
PS My house is very very quiet....no road noise etc...birdsong and the wind in the trees is pretty much all we hear unless the neighbours are on the deck (and tonight's thunder of course!)

A few more questions - please if you have the time to help me out further!

Beefing up

I"ve had a good look through the posts and haven't managed to find a pic of a cleat - am I right in thinking that a cleat, in this context, is simply a piece of timber nailed into place holding up the drywall in between the joists? (Just like the pieces - mostly 2x6 or 2x8 I think) that are there now - stopping the joists from moving/rotating?

It is my intention to use green glue on the drywall being fitted up between the joists - and am wondering - given that GG needs to be 'compressed' to be effective - whether drywall with GG on it, when being put in between the joists, should be screwed to the subfloor (to get the compression) rather than just 'held in place' prior to the caulking/ fitting of additional sheets and ultimately the cleat?

Throughout the cleat/beefing posts there is mention of 'backing rods' - are these just there to reduce the amount of caulk used - or do they play an active role in damping etc?

Ventilation

There are lots of different ventilation options on this site - dealing with lots of very different sized rooms. Given my room (within a room) is comparatively small - 2x1.6x2.45....does anyone have a suggestion for the best way to go? I like the dead vent that has an inlet and outlet with a small fan. And I assume that having a room within a room makes it a little easier (I assume the vent lies in the gap between the two rooms - but I'm not too clear!)

Thank you as ever
P

A cleat is basically anything that holds the drywall in place! strictly speaking it is a small strip of wood, maybe 3/4" square (9mm or so), nailed sideways into the stud or joist. It holds the drywall in place without needing any nails or screws to actually go through the drywall.

It doesn't need to be compressed to extremes. The GG instructions just say to "press the board against the wall or ceiling". They do also say "screws assist with the compression of the Green Glue layer into a thin film", but that's more for full sheets of drywall attached over the studs, not so much for small "between the studs" strips like you are doing. You can use screws if you want to, but that could decrease the performance slightly, and you also run the risk of damaging your floor above if the screws are too long. The cleats will hold it in place firmly enough, but it you are really concerned about this, you could build "T" shaped bars to hold each strip in place while the GG sets. Just cut a 1x3 a bit longer than the distance from floor to underside of drywall, nail a "T" piece across one end, and jam it in place. Make a few of those, so you can carry on working while the GG sets.

Both! Backer rod is just a flexible foam "tube" that you press into the joint before caulking. It creates an extra seal that you wouldn't have if you only used caulk, and also reduces the amount of caulk you need.

The best method is to instal silencer boxes in-line with your air ducts. Think along these lines:

viewtopic.php?f=2&t=1929&hilit=silencer&start=74
viewtopic.php?t=8425&start=2
viewtopic.php?f=1&t=11542&start=5
viewtopic.php?f=2&t=9761&start=0
viewtopic.php?f=2&t=11485&p=89855&hilit=silencer#p89855
viewtopic.php?f=2&t=11508&p=96578&hilit=silencer#p96578
viewtopic.php?f=2&t=13821&p=97928&hilit=+silencer+ducts+might+look+#p97928
viewtopic.php?f=1&t=15378&p=110641&hilit=+duct+silencer+#p110641

The silencers can go any place they will fit. But bear in mind that you might need access to them one day, to clean/replace the lining, fix blockages, or do other maintenance, so it would be good to put them some place where you can get at them without destroying your isolation wall!

- Stuart -

_________________
I want this studio to amaze people. "That'll do" doesn't amaze people.