Studio Construction in France

How thick should my walls be, should I float my floors (and if so, how), why is two leaf mass-air-mass design important, etc.

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faucon2001
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Studio Construction in France

Post by faucon2001 »

Hi,

As it is my first post, let me introduce myself.
I am a 53 yo sound engineer, living in France close to Bordeaux in the country side. I have read extensively this forum and now it's my turn to seek assistance for my project.

I am going to start soon the building of my studio in a new home.
The live room will be 4.62 m X 6.12 m with 2.70 m high (28 m2) and is made of 20 cm brick wall with 7 cm rock wool and 1.3 cm plaster board.
The house is hermetically sealed. It is the standard for modern construction in France.
From documentation, this wall should give around -64 to -67 dB of noise reduction.
As I want to record drums, I will need to improve this to -90 dB to comply with French regulation for my neighbors.

If I build a second wall with 2 sheets of 1.3 cm acoustic plaster board and 4.5 cm rock wool, according to supplier specs I could improve it by 20 dB, but reading the forum I learnt that a triple leaf wall is less efficient than a double leaf. In this case (brick wall + 7cm rock wool + double plaster board + 4.5 cm rock wool + double plaster board) should it be considered 2 or 3 leafs wall?

What would you recommend?
DanDan
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Re: Studio Construction in France

Post by DanDan »

Bass Frequencies pass through walls very easily, while High Frequencies can be stopped by a curtain.
So single figure dB Transmission Loss numbers have little meaning. 90dB is an extreme number, impossible at LF really.
Recording drums is about the single most difficult challenge. Think about recording with temporary drums. Programmed or played E-Drums.
Replace all or some of the sounds at the end. You will find it hard to get a better Kick or Tom recording than say the Roland V drums. Hats and Snare and Ride need to be natural.
gullfo
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Re: Studio Construction in France

Post by gullfo »

DanDan wrote:90dB is an extreme number, impossible at LF really.
only impossible if you don't have $30M-$40M to spend on it :shot:
Glenn
faucon2001
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Re: Studio Construction in France

Post by faucon2001 »

Well, I will need a huge crowd funding for this project :lol:
Electronic drum, though excellent in quality today, is not very attractive for several drummers I work with, so I really need to improve my room for acoustic drums.
In term of budget I have 10k€.

I was wrong with the specification of -90 dB. This is the first time I am doing this calculation. Let me do it again.
French regulation says that emerging noise during the day can't be more than +5 dBA
I live in the country side and ambient noise is low even during the day, around 35 dBA, so the maximum level possible by law is 40 dBA.
The brick wall + insulation + dry wall is given for -64 dB transmission loss and a drum produces around 110 dBA, so the transmission is 46 dBA.
As the distance of the live room is 8m with the garden limits, the outside level increase should be +28 dBA, meaning that the insulation is sufficient? (35+28= 36 dBA)
Am I right with this calculation ? I am suspecting something fishy with this calculation.

I understand that transmission loss depends on frequency, and that it is much lower for lows than for medium and highs. As dBA ponderation is less sensible to lows and highs, am I wrong if I consider transmission loss data at 1KHz as being a representative indicator?
Obviously, I will do measurements when I will live into the house.

So is it possible to reduce from 110 dBA to 38 dBA for 10K€ or am I dreaming ?
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Re: Studio Construction in France

Post by gullfo »

if you live in the country - does this mean you have no direct neighbors? the LF isolation is the hardest. it's also, unless it's vibrating something in the neighbors home, not as likely to be heard beyond a few meters from the building. most time noise ordinances are enforced based on complaints. not that you should be an outlaw, but it may be possible to build enough of a structure to eliminate a bunch of the sound and not impact your neighbors. also, a drum platform which isolates the kit from the floor will eliminate a lot of the transfer into the structure which would then be re-radiated. using gobos around a kit can also reduce the levels reaching the walls (and these are useful for guitar and bass amps which should also be decoupled on isolating platforms). also consider a bass guitar played via an 800W amp will likely be more likely to penetrate your isolation esp since LF can be hard to hear which is why people use massively overpowered amps... so consider the limiting of those...
Glenn
faucon2001
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Re: Studio Construction in France

Post by faucon2001 »

My closest neighbor house is 30m far from the studio, the others are at more than 100m. It's a low density residential area.
I expect to keep good relationships with them.

The house floor is made of 20 cm concrete in 2 layers with polystyrene panels in between over 40 cm of air gap. I don't know if it's good or bad. On one hand it will decrease vibration transmission, on the other it can act as a membrane and radiate more. I guess measurements will give me the answer.
I believe that the most important sound transmission will be airborne in global, the roof being the weakest wall

I once made a drum platform of a 2 cm thick sheet of MDF with tennis balls stuck to it. It was for an electronic drum played in an appartement. The neighbors were delighted, but the drummer was sea sick :mrgreen:
Are there drawings/instructions to build a drum platform somewhere in this forum? I remember to have read something about it in a thread for a drum booth, but I can't find it again.

Bass guitar is fortunately for me not an issue at all as I record with DI or amp+load box with IR, i.e in silence. The same applies for guitars.
https://www.two-notes.com/torpedo-captorx
The real difficulty is for the drum.

I don't know what gobos are. Do you mean mobile acoustic panels around the drum ? Is it a high density rock wool stuck onto a MDF sheet or something more complex?
gullfo
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Re: Studio Construction in France

Post by gullfo »

yes, the gobos (go-between) are typically absorber units with a hard side to separate amps and drums etc.

i would use a PA (or other loud capable system) to play some drums and bass music @ 110db inside and the measure the sound levels outside @ 1m, 10m and 20m to see where you need to address the isolation. mainly i would suspects windows and doors, but the ceiling/roof can also be problematic.

attach are a couple of ideas for drum platforms - a folding one using insulation (a friend needed one for stacking the kit out of the way) and another using rebonded carpet pad as the decouple. both very stable.
Glenn
faucon2001
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Re: Studio Construction in France

Post by faucon2001 »

Thanks you very much for the information. It will help.
I have found a site to simulate the transmission loss of a wall with a window, and definitely the window will be the major issue, decreasing wall insulation by 20 dB at least.

I'll be back in a couple of months with the measurements, once we move in the house. With data I'll have a better picture of what needs to be done.
DanDan
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Re: Studio Construction in France

Post by DanDan »

The A Filter is commonly used in Noise Measurement and Law. It is a historic practice, focussed on speech primarily. IMO it is pretty much meaningless with regard to Music. Distance is a factor. I remember some microphone manufacture published voltages and SPLs. A floor tom was 150dB at the typical close mic location. The most likely escapee will be the Kick drum, toms perhaps. Imagine how annoying it could be to hear just the Kick, or a muffled whole kit, starting and stopping, getting it wrong..... There is a very large psychoacoustic element here. Quiet rural is also a big factor. A client has a rural wedding venue, on a river island. It is a permanent very well built marquee structure. Wedding bands were audible 14 Miles away.
Cardioid Bass Bins and Management control of the PA system solved the problem.
faucon2001
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Re: Studio Construction in France

Post by faucon2001 »

Finally I'll be able to start the studio building soon.
As far as soundproofing is concerned, I have revised my expectations. I won't need to record drums as I have found an external solution for that. So this room will be used mainly for mixing and occasionally for individual recording.
My need for soundproofing is therefor much less.
Presently the room is built with : /20cm brick/10cm rock wool/1.3cm regular plaster board.

Initially I was thinking to add 2 layers of acoustic plaster board (2.6cm in total) to the existing walls and seal them hermetically.
The contractor I have contacted recommends to add a new structure to the existing walls : / 2cm air gap/ 5cm rock wool/2.6cm acoustic plaster board.

If I have understood correctly, the contractor proposal will add a triple leaf and soundproofing will be less efficient. Am I correct?
gullfo
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Re: Studio Construction in France

Post by gullfo »

seems likely the additional 2 layers would be sufficient if the room source levels will be reasonable (e.g. 85-90db). is the 10cm gap framed? i'm presuming it is. any concerns regarding structural (flanking)? as this may be the concern the contractor is considering.
Glenn
faucon2001
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Re: Studio Construction in France

Post by faucon2001 »

I am mixing at 80 dB and I don't push higher very often and only on a short period of time. So 2 layers seems the solution, but ...

The 10 cm gap is filled with rock wool and there is a metal frame holding it, on which are screwed the plaster boards.
I have looked at the specs for the metal posts and channels, and they recommend up to 2 layers on each side.
I don't believe that 3 layers on one side and none on the other be equivalent, and that's may be the concern of the contractor.
I am going to check it with him.

Regarding the contractor solution, do you thing it will give a better or worse sound proofing compared to 2 layers of acoustic plaster board?
The division walls inside have this structure : 1.3cm plaster board/50cm rock wool/1.3 cm

Adding the contractor solution will create a third leave. Will it ruin the sound proofing? I am a bit confused with this concept.

The contractor suggests to put rock wool with a film to block water vapor. Will it impact the sound proofing vs rock wool without film, knowing that the built walls already have this film so I believe it won't be necessary.

Do you see a better solution?
gullfo
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Re: Studio Construction in France

Post by gullfo »

having a proper vapor barrier is critical as you really do not want to risk mold - smell, sickness, etc. so if there is no vapor barrier, you may need to remove the existing drywall and get it done. the metal framing should be fine. since the exterior walls are heavy already, the two layers on the metal frame with the proper insulation should be good enough. i wouldn't go with gwb-insulation-gwb as it is likely to be less effective given flanking and third leaf effects. that said, green glue (a viscoelastic damper - not actual glue) is useful.
Glenn
faucon2001
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Re: Studio Construction in France

Post by faucon2001 »

What does gwb mean? Do you mean the contractor proposal ?
faucon2001
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Re: Studio Construction in France

Post by faucon2001 »

Talking with the contractor made me realize that he is not an expert of soundproofing. He is good for structural construction, but that's all.

I have made some drawing with the current walls, the contractor proposal, and my proposal.

If I have so far understood correctly :
- The contractor recommendation is weak due to the 3rd leaf effect. It will eat 2m2 of space and cost more.
- The proposal, seems good enough for listening at 85-90dBA max. Am I correct ?
Are 3 layers of dry wall for the outside walls necessary ?

The contractor suggests to glue the 2 extra layers with a cement adhesive. It's a rigid adhesive with a 5mm thickness applied on several spots.
I am concerned by the gap it will create between each layers of dry wall. Won't it be better to screw these extra layers onto the metal frame?

Philippe
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