Converting an attached barn in France

#1

Hi all! I’m converting an outbuilding into a practice space and am in need of some guidance. I’m in the design phase, and am feeling overwhelmed by the possibilities and am not sure which direction to move in.

Here’s the structure I’m working with:
The outbuilding is attached to the house on one end, and another outbuilding on the other. The room is 5x6m. The walls are 40cm thick rammed earth (Pisé – a traditional construction technique in my area of France). But one of the 4 walls is stone (40cm thick – this one has the other outbuilding on the other side). There’s an A frame ceiling 5.5m high at its peak, 4m high at the base. There’s a porous layer of wood and a tile roof. The room has a giant opening with a barn door of 3x4m. There’s a cement floor. There are neighbors in the vicinity as well as my attached house.

The room will be used for teaching music, rehearsing, and basic recording.

Here are my goals:
- Soundproofing as much as possible without breaking the bank – ideally I’d be able to rehearse rock groups without bothering the neighbors. If this turns out to be beyond my means, hopefully I can still rehearse softer groups.

- Have a bay window/door in the opening to let in light (the opening is south facing)

- Lower the ceiling about 2.8m high to reduce heating costs

- Keep the stone wall visible for aesthetics.

Whatever the final design, I’ll need to seal the ceiling and the barn door opening. For the ceiling, I’ll build a false ceiling either by hanging threaded rods from the roof joists or by installing wood joists into the walls. As for the barn door opening, I got a deal on a glass door/bay window, double glazed, that fits in the opening up to 2.5m height wise, then on top of the lintel, I’ll close with wood and fiberglass insulation.

After this, I see two options:

1 Insulate the false ceiling and seal everything as best as possible and potentially add an inner sliding door, and live with the results.

2 Build a room in a room. Probably wood framed structure, acoustic drywall and insulation all around and insulating the floor.

I’m still trying to come up with budgets for both plans to help me decide.

What would you do? Any advice would be helpful! I’ve attached some plans and photos for reference.

#2

Hi there Almavague, and Welcome to the forum!

The first thing I'd suggest that you do is to find out how much isolation you are getting right now (in decibels), from the current structure, then figure out how much isolation you need in order to not disturb the neighbors (as well as not having cops knocking on your door!), and also in order to not have outside sounds getting in and disturbing your rehearsal/teaching/tracking sessions.

To do that, you'll need a reasonably decent sound level meter (a real one: not an app on your cell phone), and a sound system capable of producing the type of music that you'll be making in there, at the typical levels you'll be making... or better yet, a complete live rock band, with all their gear, set up in the room playing as loud as they can. Measure the level inside the room on your sound level meter (set to "C" weighting and "Slow" response), then go outside, shut all the doors, and measure the level outside at various locations and various distances, including as close as you can get to the properties of your neighbors. Keep notes of all those readings, and the locations where you took them. At least one of those readings should be taken about 2m away from the building, in the area where the door is. That's the one you'll use as the reference point for determining how much isolation you are getting right now. The difference between that measurement and the one you took inside the room, is how much isolation you are getting at present.

To figure out the other answer: "How quite do you need it to be", you should get a copy of the noise regulations from your local municipality. That will likely specify the maximum level that you are allowed to produce, and is usually measured at the property line. There's other ways of estimating how quite you need to be, but that's the one that can get you in trouble: If your neighbor does file a noise complaint with the local authorities, that's the level they would be measuring to see if you are violating the law or not. As long as your level at the property line is lower than the level specified in the regulations, then you should be OK, but if you are above the level then you could get fined... or even shut down, depending on how bad it is, and what your local regulations say.

So, once you have those numbers, you can then figure out how much EXTRA isolation you need, beyond what you have now. And based on that, you can check the resources here on the forum to see what types of construction will produce the level of isolation you need.

That would be my suggestion: start out with the numbers, and use them to guide you to the construction.

One other thing I would definitely suggest: Do not lower the ceiling! Your building is blessed with a nice high ceiling, which is very desirable for live rooms. It think you'll find many forum members are very envious of your high roof: live rooms with low ceilings just don't sound good. There's a sort of "boxy" or "stuffy" sound to them, which cannot be fixed with treatment. So having a high roof like yours is wonderful! Do everything you can to keep it as high as possible. You'll probably lose a bit of that height with the isolation that you'll need, but it would I'd say: do your best to lose as little as possible, and keep the final inner-ceiling as high as possible.

- Stuart -

#3

Hi Stuart,
Thanks for the great response!

As for measuring current sound isolation, the barn door is extremely porous. So it seems to me any measurements I get won't tell me anything about the walls. Am I right?

As for the ceiling, you're right that a high ceiling would be better for sound. And the false ceiling could be as high as 4m. But I'm concerned about heating costs as well. I'll be heating with radiators extended from the boiler in the house. Is there a way to preserve high ceilings but minimize heating costs?

#4

Quick update on sound levels. I used a phone app (I know it's not ideal, but it's what I have at the moment.).

With a bass playing at 80db in the room:
75db 3m in front of the barn door
60db on the north side (this is a street)
50db in the bedroom

Because I'm getting about 30db reduction between the room and the bedroom, I suspect that if I simply close up the room (sealed false ceiling, and door), I would probably get roughly 30db reduction all around. I read that standard double glazed doors give about 35db of reduction.

These are clearly ballpark figures. But does that sound about right?

#5

That's a start, but you should really set up a full-range system and play typical full-range rock music to do your testing. If you test with just a bass, then you are only testing a very small part of the spectrum, and in a region where ears aren't even that sensitive (and isolation is generally terrible anyway).

So, the fact that you are getting 75 dBC outside the door with an 80 dBC source, does indeed indicate that you are getting no isolation at all from the door! However, at typical bass frequencies (maybe 40-80 Hz), the expected isolation would be pretty low anyway. Also, 80 dBC is nowhere near loud enough to be realistic. A full rock band playing hard is probably putting out about one thousand to ten thousand times the intensity (in other words, more like 110 dBC to 120 dbC). Just the drum kit alone, played hard and fast, can put out 115 dBC without any sweat

Full spectrum measurements at typical rock band sound levels would give you a better indication of isolation.

It's also important to measure at the location on your property line that is closest to where your neighbors are located. That's they critical point. That's where the cops or municipal inspectors would measure if there ever is a noise complaint.

How far away is that point from the wall of your barn? This is also important, because distance is your friend here. Sound dissipates at a rate of around 6 dB each time you double the distance. That's in theory, but in practice in typical urban areas, it is usually more like 4 or 5 dB drop with distance doubling. So if your neighbors are 100meters away, then that's great! You get a lot of noise reduction just from the distance. But if they are only 5m away, then you get very little benefit.

I would probably get roughly 30db reduction all around.

30 dB is about what you get from a typical ordinary house wall, ... with luck. 30 dB is not very much at all. Assuming typical "jamming hard" rock band level of 120 dbC inside the studio, you'd have 90 in the bedroom. That's LOUD! Your neighbors would also be getting around that, or more (depending on how far away they are). Certainly noise complaints coming your way! Most residential noise regulations specify a limit of something like 40 dB during the day, and 35 at night...

Here's something I wrote about determining isolation, a while back: How much isolation does your studio need? How can you figure that out? Is it even important?

About the heat issue: Isolating your building acoustically (often called "soundproofing", which isn't a good term for describing it!) implies that you will also be using a LOT of thermal insulation in between the two sides ("leaves") of your walls and ceiling. That will help a great deal to keep your room thermally isolated, as well as acoustically isolated. Many recording studios don't need much heating at all, and instead need cooling, even when located in cold climates, simply because they are so darn will insulated. You might need a bit of heating when you first start up in the morning, but with several people, equipment, lights, etc. in there, it can warm up quite fast, and then you'll need to get the HVAC switched over to cooling, rather than heating.

I'll be heating with radiators extended from the boiler in the house.

Radiators are noisy, for studios. Water movement, thermal expansion "clicking", etc. Not good when you are tracking instruments. And since you will need a complete HVAC system anyway (read this: Myth: "My studio does not need HVAC" ), it would be better to save your money, not invest in all that plumbing, and instead put that towards the HVAC system. There's more about the types of HVAC that you might consider, here: Studio HVAC: All about mini-split systems, HRV's and ERV's

There's several other resources in the reference area that you might find useful.

- Stuart -

#6

Thanks a million Stuart for your response!

Let me ask a different question:

What amount of isolation would I get doing a room in a room set up, with 2 double glazed bay windows/doors (2.5m x 2.5m) and say, 30cm between them? If each door gives me 30db of reduction, would that double using two of them?

Or if I put a glass door on the outside, and found another system on the inside (double doors, or some sort of industrial sliding door for example), then I could open the heavy door to get in light, then close it when I need sound isolation.

I realize people don't typically install bay windows/doors if they want sound isolation, but this space will be used probably more for teaching/working than for rocking. It's the only space in the whole house that can get direct sunlight, and I think it would be a real shame to close it.

Any thoughts?

#7

Almavague wrote:Source of the post
What amount of isolation would I get doing a room in a room set up, with 2 double glazed bay windows/doors (2.5m x 2.5m) and say, 30cm between them? If each door gives me 30db of reduction, would that double using two of them?

Not really, no, because there are other things going on inside the cavity. It's not as easy as just adding up the individual isolation numbers.
For any given two-leaf barrier (such as you would be making with your two glass doors), there are actually four different "regions" across the audible spectrum, where each region has a different level of of isolation, governed by different physical characteristics. Here's what the isolation "curve" typically looks like for such walls:

For the very lowest frequencies, the dominating factor is how stiff the wall is. Next up is the complicated part: resonance. At some specific frequency (which depends on several factors too!) the wall will resonate. That is its natural resonant frequency, and at the specific frequency the isolation goes down to a minimum value. In some cases, isolation can even be negative (in other words, the resonance is so bad that the wall actually amplifies sound at that frequency). Going further up the scale (once you get beyond the resonant area), it is basically the mass of the wall that dominates, and in this area yes, you can more or less add up the isolation numbers for each of the leaves (wellllll.... sort of!). Until you go further up the spectrum and get to the coincidence dip. This is another resonance-related issue, that' a little harder to explain, but basically it is related to the speed of sound in the materials that the wall is made of, and the angle that the sound wave hits the wall. Complicated. But at the frequency range, once again there's a drop in isolation. Above coincidence, mass is dominant once again.

There are equations for calculating all of these, and thus predicting the performance of any give wall, but really the critical issue is that resonance thing in the low end of the spectrum. That's your biggest problem. With a two-leaf wall, that frequency is mostly governed by three factors: mass, cavity depth, and damping:
"Mass" is simply how heavy the walls area (measure by surface area. So for example kg per square meter, or pounds per square foot). You can figure that out very easily just be looking at the cubic density of the materiel that your wall is made of (in your case; glass), and dividing by the thickness.
"Cavity depth" is the distance across the interior air of the wall: between the surface of the outer leaf and inner leaf. In your case, between the outer glass and inner glass.
"Damping" is whatever acoustic damping material you have inside the wall. For ordinary walls, that is usually mineral wool or fiberglass insulation, but obviously you can't do that between window panes! So for a window or pair of sliding glass doors, there is basically no damping at all. Thus, the only two factors that you can control, are the mass and cavity depth. More mass is better. more cavity depth is better. Both of those force the resonant frequency down lower in the spectrum. Ideally, you want the resonant frequency to be at least an octave lower than the lowest frequency that you need to isolate.

OK, that's a very long, convoluted way of saying: No. You can't just add up the individual isolation numbers to get the total isolation. You have to use a set of equations to do that, which takes a little while!

- Stuart -

#8

Great, thanks!

What would be a good distance for the cavity? I was shooting for something like 30cm, but if I went up to 50cm, would that be worth the loss of space in the room? Maybe another way of asking the same question is: what's the equation to calculate sound isolation related to cavity depth?

#9

Almavague wrote:Source of the post Great, thanks!

What would be a good distance for the cavity? I was shooting for something like 30cm, but if I went up to 50cm, would that be worth the loss of space in the room? Maybe another way of asking the same question is: what's the equation to calculate sound isolation related to cavity depth?

The actual equations for MSM are in this article that I wrote a while back, along with some additional info that you might find useful:

What is MSM? How does it work?

As you can see, cavity depth is part of it, and mostly changes the resonant frequency (bigger cavity = lower frequency), but the actual frequency also depends on the mass on each of your two leaves. The mass is also mostly responsible for the actual isolation, but it's a complex relationship. The equations in that pot should help you decide on how big your cavity needs to be. But do make sure there is only one cavity inside your wall! Not two, not three. Just one. In other words, make sure that you have only two leaves. That's important. Extra "leaves" inside the wall will reduce your isolation, not increase it, for the reasons in that article.

- Stuart -

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