recording studio in a brick stable

[alfkalf]

hi,
I’m building a recording studio in an old stable. The walls are plain bricks (44cm width).
The stable is 14m x 5 m inside the walls (70m2) and there's 3,3m to the ceiling.
On the right of the stable, there is the horse boxes with IPN (18cm) and brick vault ceiling and on the left, there is the garage with 2 big doors and a stud (17cmx7cm) + plaster (3cm) ceiling.

0stable VE.png

There’s a flat at the first floor and the neighbors house is at 10 meters from the stable.

1maison voisins.JPG

I broke the middle transversal wall, move the stairs to a new staircase at the extreme right of the building, dug to make independant concrete floors.

2 mur transversal.png

4 interieur.png

3 preparation dalle.png

6 cage d'ecalier.png

My goal is to make a one room recording/mixing studio with one small booth and to keep a maximum of windows and a french window to have natural light. I walled the doors left.
I would like the noise to reduce for the flat above (but I don’t want a total silent place above).
Nevertheless I don’t want the neighbors to hear the music even at night.
I record any type of instrument (piano/drums/guitars etc...) most of time separately and I would like to mix on the right and record on the left in the house.

Floor plan 2.png

here’s my questions :

Inner walls and ceiling. (height=2,80 to 3m)

the carpenter suggests to make inner wall with OSB (18mm), timber frame (120mmx45mm - 67cm between studs), wood wool insulation (120mm), and OSB (18mm)
joist (120mmx45mm) and idem for the ceiling

if I look at John’s recommandations the timber frame is smaller (75mm vs 120mm) each 45cm and would be insulation (45mm)/plaster/plaster(16mm)/timber frame (75mm)/insulation inside frames)

1) what are the advantages of john’s solution. What do you thing about my carpenter suggestion ?
2) what is the best way to avoid low frequencies to go to my neighbors. Is there a physical rule between low frequencies attenuation and surface mass walls and distance between inner and outer walls?
3) Do you think a 75mm width wall is enough to support a 5 meters width ceiling (about mass)
4) How can I do to avoid condensation and moisture between inner wall and 44cm outer brick wall?
4) what do you thing concerning wood wool vs rock wool?

best regards

[Soundman2020]

Hi Yannick, and Welcome!

dug to make independant concrete floors.

So you need a lot of isolation?

I don’t want the neighbors to hear the music even at night.

OK. But do you have a number yet? By "number", I mean a goal for how much isolation you need, in decibels? That's that's starting point for designing an isolation system.

My goal is to make a one room recording/mixing studio with one small booth

But the diagram shows TWO rooms, not just one: Is the other one for storage?

I would like to mix on the right and record on the left

With reference to the way your diagram is posted here? In other words, you want to set up your speakers, console and desk right where the doors are to the two isolation booths? That would not be a good idea, because that part of the room is not symmetrical, and the doors would be interfering with the speakers. It would be better to set up the "control room" part of your studio facing the other wall, at the left end of the diagram.

Also, that single room is very long and thing: it is NOT a good set of dimensions for a control room. In general, a control room should never be more than about 2.5 times longer than the width. The modal response just becomes so bad beyond that... It might be a good idea to divide it into two rooms.

the carpenter suggests to make inner wall with OSB (18mm), timber frame (120mmx45mm - 67cm between studs), wood wool insulation (120mm), and OSB (18mm) joist (120mmx45mm) and idem for the ceiling

That would be a bad idea, as it would create a three-leaf system, which means that your low frequency isolation would be worse, not better.

if I look at John’s recommandations the timber frame is smaller (75mm vs 120mm) each 45cm and would be insulation

(45mm)/plaster/plaster(16mm)/timber frame (75mm)/insulation inside frames)

Correct. That gives you a 2-leaf system, which has much better isolation for low frequencies. The size of the framing is not so important, acoustically: you can use 120mm studs if you want. The plasterboard ("drywall") is more dense than OSB, so 16mm thick plasterboard is heavier than 18mm OSB.

1) what are the advantages of john’s solution. What do you thing about my carpenter suggestion ?

The advantages are that it is a two leaf system (not the three-leaf proposed by your carpenter), and it has more mass where it belongs. So it will give you better isolation for lower cost.

2) what is the best way to avoid low frequencies to go to my neighbors.

By building a two-leaf MSM isolation system, with a lot of mass on both leaves and a large air gap, filled with suitable insulation of the correct type and density.

Is there a physical rule between low frequencies attenuation and surface mass walls and distance between inner and outer walls?

Yes:

double-triple-equations-GOOD!!!! f0.jpg

There you have both equations, for a 2-leaf wall first, then for a 3-leaf wall. As you can see, the resonant frequencies for a 3-leaf wall will always be higher than for the equivalent 2-leaf wall, and therefore the isolation will be worse.

3) Do you think a 75mm width wall is enough to support a 5 meters width ceiling (about mass)

As far as I know, John uses 2x4 studs, which measure about 40mm x 90mm, roughly. If they are spaced correctly, and the wall is sheathed correctly, then a stud walls built like that should have no problems supporting a ceiling that spans 5m. However, 2x4 joists would not be suitable for spanning 5m. You would probably need at least 2x8's for that, and maybe even more. But only a qualified structural engineer can tell you for certain: you will need to hire one.

4) How can I do to avoid condensation and moisture between inner wall and 44cm outer brick wall?

You build it correctly! You need to make sure that your wall has only one vapor barrier in it, and that must be on the warmer surface of the wall cavity, and you probably also need one or more water barriers, and one or more air barriers: They must all be placed in the correct locations in the wall, according to your local climate and building codes. Do not guess! If you do not know where they need to be for your climate, then you should find out from your local municipality, and local building contractors.

4) what do you thing concerning wood wool vs rock wool?

For insulation? I imagine that by "wood wool" you mean "cellulose fiber"? I would always prefer mineral wool (rock wool) or fiberglass insulation.


- Stuart -

[alfkalf]

Thanks a lot for your answers. It's very interesting.

concerning the floor plan.
right end, above : a recording booth
right end, below : the stair case
ok for your feedback concerning the studio setup.

About soundproofing :

You talk about a number, i.e. a transmission loss (dB). Unfortunately, it's a real problem to determine this number. More over, this number depends on the frequency. I would not like my (10 meters) neighbors to hear the drums but I can't convert this in dB.
It would be very interesting for me to know this number to buy the doors and the windows too. You could evaluate this number with your experience?

I didn't know double or triple leaf concept.
It means that each air cavity "creates" a low resonant frequency which reduce the transmission loss for this frequency.
And your formula shows that if we add another MSM, this frequency increases?

1) I walled doors and I build staircase with hollow blocks
I guess it was not a good idea because it will create at this place a triple leaf as soon as It will be an inner wall (because of the air cavity in the hollow block)? I should have use plain blocks i think?

2) Is it the same (in a 2 leaf system) to place the plaster sheets inside or outside the inner wall?

3) ok for the dimensions of studs.

4) Wood wool is not cellulose fiber. It's the literal french translation, I don't know the English word for this but it's look like this :

panneaux-semi-rigides-laine-de-bois-270882.jpg

regards

[Soundman2020]

You talk about a number, i.e. a transmission loss (dB). Unfortunately, it's a real problem to determine this number.

Actually, it is very easy! You just need a hand-held sound level meter. Get a typical band together and ge them to play at the typical level that you expect to have in your room, and measure that level with your meter. That sets the level of "How loud are you?". Then send them home, wait until the quietest time of day or night in the location where the studio is, and measure that level. That one sets the level of "How quiet do you need to be?". Subtract the second number from the first number. Bingo! You now have the single number that tells you "How mush isolation you need", in decibels. Not hard at all!

More over, this number depends on the frequency.

No it does not! It only depends on you measuring it, which you do with a decent quality sound level meter, set correctly and used correctly. Set it to "C" weighting, "slow" response, hold it at chest height, away from your body, with the mic pointing upwards at an angle of about 45°. As long as your test is done using a band and music that is representative of the types of bands and types of music that you will be tracking, then your results are valid when measured like this, and can indeed be described with a single transmission loss number, independent of frequency.

I would not like my (10 meters) neighbors to hear the drums but I can't convert this in dB

Yes you can. And if you don't, then your isolation plan is doomed to failure. If you do not know what you are aiming for, you certainly will not get it!

The starting point for any successful studio design is to set the basic parameters that you are aiming to achieve. That's how we studio designers do it: We start out by determining how much isolation is needed, what the acoustic response should be, what levels to expect, room occupancy, climate conditions, and several other basic needs that can be defined with simple numbers. Then we use those numbers to design the structures and systems that will produce the required outcome. The goal has to be measurable, and fortunately most aspects of studio can be specified and measured with simple objective numbers.

If you don't know what you want, then you won't get it. It really is that simple. If you do know what you want, then your chances of getting it are much, much better.

It means that each air cavity "creates" a low resonant frequency which reduce the transmission loss for this frequency.

Correct. In fact, at the resonant frequency of that cavity, the wall does not isolate at all. It only isolates starting from 1.414 times the resonant frequency. So the design goal is always to tune the resonant frequency of the wall at least one octave below the lowest frequency that needs isolating.

And your formula shows that if we add another MSM, this frequency increases?

Correct. There is interaction between the two resonances, there are two resonant frequencies for a three-leaf wall, and BOTH of them are higher than the single resonant frequency for the equivalent two-leaf wall. And the slope of the isolation curve also changes.

I guess it was not a good idea because it will create at this place a triple leaf as soon as It will be an inner wall (because of the air cavity in the hollow block)?

It's not too bad, since the two leaves are very firmly coupled together by the sides and webbing of the blocks, so that acts more like a single leaf than it does like a two-leaf. There is also a lot of mass in those blocks, and they are very rigid. All of that helps.

I should have use plain blocks i think?

Or you could just fill the hollow spaces in the blocks with sand. Sand is a very good acoustic damping material, and also adds a lot of mass. Many people do "sand filled" walls for this reason. If you still have access to the top of the wall, you might still be able to get sand in there.

2) Is it the same (in a 2 leaf system) to place the plaster sheets inside or outside the inner wall?

Yes. The location of the studs makes no difference: the only purpose of the studs is to hold the plasterboard in place. What matters (as you can see in the equation) is the distance across the cavity between the two leaves. That is one of the key elements in MSM walls. As long as that distance is big enough to give you the correct resonant frequency, then it doesn't matter if you have the studs on the inside the wall cavity, or inside the room.

However, there is an advantage in saving space to have the studs in the room, because that allows you to use the stud space for acoustic treatment in the room. If you have the studs in the cavity, then you would need to build treatment panels and hang them on the walls, but if you have the studs in the room, then you can build the treatment in between the stud bays, using the studs themselves in many cases, thus saving on materials as well.

4) Wood wool is not cellulose fiber. It's the literal french translation, I don't know the English word for this but it's look like this :

It looks like some type of particle board? Is it made from wood chips, sawdust, or something like that? If so, then no, it would not be a good acoustic damper.

- Stuart -

[alfkalf]

Hi,
Thanks a lot. Very interesting.
My SL meter device gives (C/Slow) at 3 meters from the source :
105 dB for drums. 115 in front of it
87 dB for the grand piano, 95 in front of it
I don't think I will reach more than 115 dB with a band. More over it would be very occasional. Anyway my goal is to play the drums at night.

I've just measured 22 dB outside. It's a quiet night with some wind and some cars on the road at 400 meters from here.

105-22=83 for the drums?
if the neighbors are at 10 meters from the house there's an adding attenuation of 10 or 20 dB (distance attenuation)?
can we say this?
my number would be 63? 73? for the drums at night.


Concerning the flat above, I have 20 dB inside the rooms. 105-20=85dB.
So the number for the flat would be 85 dB?

Anyway, the most important think is the neighbors.

Is it ok (I don't know if I should have measured at 3m or 1m)?


regards

[Soundman2020]

105 dB for drums. 115 in front of it ... 87 dB for the grand piano, 95 in front of it
I don't think I will reach more than 115 dB with a band. More over it would be very occasional. Anyway my goal is to play the drums at night.

115 is about right. That's more or less what a normal to loud band plays, so take taht as your peak.

I've just measured 22 dB outside.

22 is pretty low: What meter are you using? Not many SPL meters go down to 22 dB. What brand and model is it? Are you sure you had it set to "C" weighting, and "slow" response?

105-22=83 for the drums? if the neighbors are at 10 meters from the house there's an adding attenuation of 10 or 20 dB (distance attenuation)? can we say this?
my number would be 63? 73? for the drums at night.

Theoretically, there is a reduction of about 6 dB each time you double the distance, which works out to a drop of approximately 20 dB for ten times the distance. So if you cold isolate your studio such that you get 55 dB measured 1 m from the wall, in theory you should be getting 35 dB at a distance of 10m from the wall. There are a lot of assumptions in that "rule", but it gives you a rough idea.

A level of 35 dB is almost inaudible for most people in most situations, because there is virtually always some background noise, even in very quite locations, that will mask quiet sounds. One frame of reference says that if you were to measure in the middle of a desert, on a very calm night with no wind, that would be about 20dBC. A very quiet bedroom might be 30 dBC. So if you can get your level down to 35 dBC at the wall of your neighbor's house, it's pretty sure that they won't hear you at all, inside.

OK, so assuming you are aiming for that level (35 dBC at your neighbor's wall), 55 dBC outside your studio wall), and assuming that your peak level is 115 dB, then you'd need about 60 dB of isolation. That is possible, but it needs a lot of work and careful design to get that much isolation. Most project studios and home studios aim for about 50 dB. 60 is doable, but needs care.

As a point of reference, a typical house wall (wood studs with drywall on each side) will get about 30 dB of isolation, but the decibel scale is logarithm, not linear: each time you go up 10 points, you multiply the intensity by a factor of ten. So increasing from 30 dB to 40 dB means that you need to block 10 times as much energy. Going from 30 dB to 50 dB means that you need to block 100 times more energy. And going from 30 dB to 60 dB means that you need to block one thousand times more energy than a typical house wall.

Concerning the flat above, I have 20 dB inside the rooms. 105-20=85dB. ... So the number for the flat would be 85 dB?

85 dB of isolation is very, very hard to do. I'm skeptical that the level in the flat upstairs is only 20 dB: that is beyond the capability of most sound level meters to measure. Most can only measure down to 30 dB. You need exceptional electronics and an exceptional mic to measure that low, accurately. The meter might be telling you that, but I doubt that it is correct. Most meters only go down to 30 dB. That's why I'm so curious about yours, which claims to be able to measure 20 dB.

So, to summarize: If you want to record drums at any time of the day or night, without disturbing your neighbors, then you will need about 60 dB of isolation. It is possible to get 60 dB of isolation, and your existing building is a very good starting point because it has very dense, heavy, massive walls floor and ceiling. It should be possible to get 60 dB with your place, if the inner leaf is designed and built correctly. The weakest parts will be your doors, windows and the HVAC system. Getting 60 dB isolation for those is not easy at all. Doors especially, because the have to open and close, and HVAC because it has to allow the movement of air while blocking sound.

So that's the situation: What you want can be done, but it will need to be designed very carefully, and built very carefully.

- Stuart -

[alfkalf]

I should have talk about my SL device. Here's my device

Sphynx.jpg

You're right for the low values. I have no value under 50 dB (I see LO). I used a smartphone with the sonometer app. and take the average 30s value and I guess it's not accurate. Sorry for that!
if it's 20dB in the desert, I think it's a lot more here and my value is false. I'm in a wood area with a road at 400 meters.

This morning with the sphynx device, I can measure between 52 and 56 (there are a few more cars, some planes and wind through the leaves) even 60dB with birds and I have the feeling it's quiet. I guess I was just below 50 at night.

Hence, I could probably try to reach 50dB for my number and it will be very good.
Moreover, there will be an outside cooling system unit with fans and it will add some noise more.

Even if the house is a good starting point for floor and walls, I'm not sure for the ceiling.
On the left, above the studs + plaster there is an old solid wool flooring and no insulation.

IMG_5108.JPG

On the right, the brick vault ceiling is not really thick (may be 2 layers of 3 cm thickness) between 18cm metal IPN. above this system, there are joists and the solid wool flooring. (no insulation between joists)
Here's a picture showing both systems where was the old stairs at the middle of the room.

IMG_5087.JPG

VAULT

2015-09-18 09.02.01.jpg

2015-09-18 09.00.12.jpg

Thanks