Studio Control Room Ireland, help needed with soundproofing

Posted: Fri Jul 18, 2008 3:38 pm

Hi Everyone,
My name is hally and I am located near Dublin in Ireland…
I am at the planning stage of my studio build and need help making a few decisions on how I propose to isolate the control room from the rest of the dwelling. The control room will be used for mixing music; it will also act as a video editing suite and for recording acoustic instruments and vocals. I also wish to construct a machine room adjacent to the control room. On completion of the control room I will be starting construction of the rest of the studio, 2 live rooms, toilet, and green room. The Control also needs to be sufficiently soundproofed to eliminate as much sound coming from the live rooms.

I previously posted my plans for the whole studio which includes other areas of the building (live rooms, etc) but I became so overwhelmed by the entire project I have decided to work on a room by room basis. This suits my head and my budget. It also means that when this control room is complete I can move in to begin work while continuing to build the rest of the studio.

My main goal for the Control Room which is an attic space is to limit outside noise (dogs, heavy vehicles, etc) from entering the room and isolate the noise within the room from the rest of the dwelling. The sound levels within the CR will be generally at normal mixing/ recording levels. The work to date carried out on this attic room has been to create an entrance into the room through what used to be a 12” Cavity gable end wall and the installation of a timber stairs leading up to this entrance. As you will see in the pictures below the room is bear, a blank canvas you might say.

Room Dimensions: W 12’ X L 24’ X H 7’8” @ the apex of the roof.
Floor Square footage: 288sq feet
The Roof: Tiles sitting on 2 X 1 battens on felt on rafters on 8” x 3” purlins…
The Block Walls: 12” Cavity Concrete walls, consisting of (from the exterior inwards) Plaster Skim, 4” block, then cavity, then aerobord, then 4” block. (cross section pic. below)
Rafters: 5” X 1 ½” @ 16” centers, 18 rafters running each side of the apex.
Floor Joists: 7” X 2” @ 16” centers. These joists are supported (sitting on ) the exterior walls and they span to about half way across the width of the building where they are nailed together and sit on an internal 4” block wall below.
Partition Wall: 3” X 1 ½” Stud partition acting as perlin to support the rafters. I have been advised by an engineer that it is possible to move this wall back 4’ by inserting a Reinforced Steel Joist to extend the width of the room to 16’.

Here are a few floor plans, pictures and 3D shots of the room
Aerial Views of the attic space and machine room

http://www.jamesmmedia.com/controlroom/cr-aerial-2.jpg
http://www.jamesmmedia.com/controlroom/cr-aerial-1.jpg

Cross Section Drawing of the Back of the Building
http://www.jamesmmedia.com/controlroom/cr-back-section-house.jpg

Floor Plan Drawing
http://www.jamesmmedia.com/controlroom/cr-floorplan.jpg

Photographs of the Room as it is now
http://www.jamesmmedia.com/controlroom/controlroom-entrance-view.jpg
http://www.jamesmmedia.com/controlroom/cr-view-from-window.jpg
http://www.jamesmmedia.com/controlroom/cr-entrance-machine-room.jpg
http://www.jamesmmedia.com/controlroom/cr-rafter-detail.jpg
http://www.jamesmmedia.com/controlroom/cr-staires-landing.jpg
http://www.jamesmmedia.com/controlroom/wall-crosssection-detail.jpg

If anyone requires more details about the structure of the building don’t hesitate to ask, I have drawing plans of concrete slab foundation, etc.

Testing with Sound level Meter
I hooked up a pair of speakers in the room below the attic space and played a drum loop and a deep bass pattern through them. The sound level meter was set to slow dBC reading and the level next to the speakers was max 103.3 dBC. Upstairs the meter read 87dBC and the floor joists were buzzing (it was a very deep bass sound) The reading in the attic normally without music blasting from below with normal everyday passing traffic, water tank, birds, etc was from 47 – 55 dBC.

My Plan for Soundproofing
1. To treat the Floor of the attic/ Control Room I am considering following Rods guidelines from his book. My joists as they are do not have any cross bridging…
http://www.jamesmmedia.com/controlroom/joist-detail-1.jpg
http://www.jamesmmedia.com/controlroom/joist-detail-2.jpg

2. For the existing partition wall made from 3” X 1 ½” Studs (this wall cannot be moved as it is load bearing) I thought I would again follow Rods guidelines by adding another 3” X 1 ½” Stud partition behind it with air space between them, both these walls will be sitting directly onto the joists.
http://www.jamesmmedia.com/controlroom/wall-partition-detail.jpg

3. The existing cavity block walls, it has been suggested to me that the STC of these walls would be pretty good as they are, so I thought I would just add one layer of plasterboard for aesthetic reasons. Ideally I would like to insulate these block walls with some fiberglass behind the plasterboard but this would mean erecting some studs on the walls and I think I would be then creating an extra leaf to the wall.

4. The roof, this is really tricky and to be honest I am lost as to the best way to approach it. The building regulations here in Ireland state you must leave a 50mm gap between the roofing felt and whatever insulation you put in the roof. This is to allow the roof to breed and something to do with condensation (i think). Head room is at a premium in this room so I am unsure what my options are. But to start the ball rolling here’s what I’m thinking. Roof Tiles, felt, air gap, 2 layers of 9mm or 11mm plasterboard, standard fiberglass, resilient channels, 2 layers 9mm or 11mm plasterboard. All sealed appropriately. Below is a cross sections drawing of the proposed roof treatment….

http://www.jamesmmedia.com/controlroom/roof-soundproofing-cross.jpg

My Questions;

THE FLOOR
1. Is the treatment for the floor of this room the best option or should I be considering other methods?
2. Assuming my suggestion for the floor is the best way to go is it safe to assume that the 7” X 2” floor joists @ 16” centers will have no problem in carrying the extra load?
3. Currently there is no bridging between the floor joists, should this be still be installed after the plasterboard has been put between the joists?
THE PARTITION WALL
1. Is my approach here the best option?
2. Behind the existing single layer of plasterboard there is a thin sheet of plastic, does this need to come out and should I just remove the single layer of plasterboard and start with the new installation?
THE EXISTING CAVITY BLOCK WALLS
1. Again, are my proposals for these walls ok, any suggestions welcome?
THE ROOF
1. I am really just guessing as to how to treat this section of the room and because it covers such a large surface area of the room its imperative that I get it right, please advise as to my best options here?
GENERAL
1. Should I be thinking about altering the internal shape of the room, ie. Slanted walls, etc.

Thank you for taking the time to read my post and I look forward to your responses and advise.
Warm regards
hally

Posted: Sun Jul 20, 2008 9:39 pm

The amount of questions you are asking is almost an entire acoustical project.

From what I've seen, that room in an inverted V shape could be a nice small tracking room. If you want to turn it into a CR, you can use acoustical blankets and cloth - > create an acoustical ceiling.

Use dB(A) or just flat dB, instead of dB(C). nobody uses dB(C) except for very high sound pressure levels. I understand you are using dB(C) due to the low frequency contents of music, but for environmental acoustics, if you want to evaluate the background noise of a room, due to traffic noise, you should use dB(A). Or just use flat dB if you want to analyze the sound insulation from one place to another.

Posted: Mon Jul 21, 2008 11:52 am

Thanks for your responce, I wouldn't exactly call the room small, its 25f x 12f x 8f approx and it has to be the control room given the premises in question...

"The amount of questions you are asking is almost an entire acoustical project"
how do u suggest I word my questions? I have put alot of time and effort into researching this project and the forum moderator expressly requests that we give as much detail as possible. I apologise if my post is a little long winded but I am simply trying to cover all angles.

Thanks for the info on testing, i will redo my test and post results

regards hally

Posted: Mon Jul 21, 2008 4:13 pm

Although by the standards of home studios this room is slightly mid sized (small = less than 2,000 cf) acoustically speaking this is a small room.

Everest (Master Handbook of Acoustics 4th Edition -on Page 419) lists mid size rooms acoustically in the 3,400 cf range - and large in the 8,000 cf range..... so 2,400 cf isn't very large at all.

Sincerely,

Rod

Posted: Mon Jul 21, 2008 6:06 pm

Thanks Rod,
any thoughts on my ideas for soundproofing this space.
I would like to take this opportunity to thank you for your wonderful book, i had read several other publications which only seemed to add to my confusion but yours was clear and simple. Keep up the good work,
warm regards
hally

Posted: Mon Jul 21, 2008 6:11 pm

Hi Rod
forgot to add, i can post images of the whole building to give u an idea why i have chose thid space as the control room if they would help...

thanks hally

Posted: Mon Jul 21, 2008 8:51 pm

Hally,

I'm going to get to what I am thinking about. Some of the simple things are...the more load you place on this upper area the more support it will need below floor level.

If you move a wall there should be a wall constructed directly below it, and a foundation below that to the ground.

That said, any loading up of this roof you do places more outward pressure on the existing wall system. Especially if support underneath has not had the utmost attention.

You can collapse a structure if it becomes top heavy. Worse case scenario I know, but it has to be said.

All things considered, my opinion, you require someone local to you to aid you in structural support of this proposed build first and foremost.

Brien

Posted: Tue Jul 22, 2008 3:31 am

Thanks Brien, so just to clarify, I should use the plans I have already for soundproofing, present these to my local surveyor and take it from there...

My only reason for moving the partition wall was if it was going to have some acoustical benifit for the room, otherwise i am happy to leave it where it is...

thanks alot hally

Posted: Tue Jul 22, 2008 6:24 am

Sometimes you soundproof a room where there's no need to do so... this depends on:

a) pressure levels in the room
b) exterior noise
c) distance to neighbors

What do you want to record ? Is your goal just to build a decent Control Room and mix your stuff in it ? You have stated 103 dB(C). That is quite high pressure level volumes and I highly doubt you will mix/master during continuous hours at those volumes (and adding the risk of becoming deaf).

Environmental noise is measured in dB(A) which is an hi-pass filter. This has some immunity to low frequency sounds. Maybe you can do that test again with the sound level meter using dB(A). You should check what are your noise limits in your country. Here is 45 dB(A) at night and 55 during day

Posted: Tue Jul 22, 2008 11:23 am

Hi andre,
"You have stated 103 dB(C). That is quite high pressure level volumes and I highly doubt you will mix/master during continuous hours at those volumes (and adding the risk of becoming deaf). "

those readings were done with a drum loop blasting out of my speakers from the room directly below which will in time be a drum recording room. I monitored the level in the room with the speakers and it read 103dB(C) and i then monitored the level in the attic space in question and it read 87dBC. I will test again with the correct settings on the meter and post my results later.

"What do you want to record ? Is your goal just to build a decent Control Room and mix your stuff in it ?"
Yes to build a decent CR room where I will record music from the 2 other live rooms in the building which are located below the control room on the ground floor. Types of music will vary, but mainly acoustic and occasionally drums. My main consern with the CR is to eliminate external noise and contain normal mixing level sound within the room as part of the building is a residence and i do not want to disturb the occupents.
I will do my testing and get back to you
thanks for your input, regards hally

Posted: Tue Jul 22, 2008 11:50 am

Hi,
The New Test Results

Sound Level Meter Settings
dBA, slow.

Standing in the middle of the attic space with normal everyday sounds, birds, distant traffic, etc the meter read 33.5 dBA.

Standing in the room with a drum loop blasting from room below the Attic space @ 92 dBA the meter read 57.3 dBA

I hope these are the right settings

regards
hally

Posted: Tue Jul 22, 2008 2:01 pm

Hally,

mixing is generally done around 85 dB - anything above that is too loud - and anything below that is tiring because you are fighting to hear everything.

Sincerely,

Rod

Posted: Tue Jul 22, 2008 4:05 pm

Heavy traffic streets are usually around 65-75 dB(A) LAeq. If you want an NRC 20 in the studio that's perfectly executable.

Posted: Tue Jul 22, 2008 4:12 pm

Thanks to everyone so far for their input. I have booked a structural engineer to come and have a look this friday.

The questions I will be asking him are

1. Will the existing floor joists support my proposed soundproofing materials?

http://www.jamesmmedia.com/controlroom/joist-detail-1.jpg
http://www.jamesmmedia.com/controlroom/joist-detail-2.jpg

2. Will the existing rafters support the extra layers of plasterboard I want to install?
http://www.jamesmmedia.com/controlroom/roof-soundproofing-cross.jpg

3. If in either or both cases that extra support is needed, what needs to be installed?

4. Is it safe to add more mass to the existing partition wall and to add another partition wall closely parallel to it?

http://www.jamesmmedia.com/controlroom/wall-partition-detail.jpg

Are there any other questions anyone can think of that i need to ask?

thanks hally

Posted: Tue Jul 22, 2008 5:43 pm

Quote:

Are there any other questions anyone can think of that i need to ask?

The enginner should be the person asking the right questions........

Rod

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