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PostPosted: Wed Mar 10, 2021 3:43 am 
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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?


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PostPosted: Thu Mar 11, 2021 2:24 am 
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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.

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http://www.irishacoustics.com
http://www.soundsound.ie


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PostPosted: Thu Mar 11, 2021 3:52 am 
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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:

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PostPosted: Thu Mar 11, 2021 6:04 am 
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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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PostPosted: Fri Mar 12, 2021 2:27 am 
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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...

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PostPosted: Sat Mar 13, 2021 4:39 am 
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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?


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PostPosted: Sat Mar 13, 2021 6:50 am 
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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.


You do not have the required permissions to view the files attached to this post.

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PostPosted: Sun Mar 14, 2021 2:44 am 
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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.


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PostPosted: Sun Mar 14, 2021 5:50 am 
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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.

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http://www.irishacoustics.com
http://www.soundsound.ie


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