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Author Topic: isolation / common walls  (Read 1214 times)

i dig music

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isolation / common walls
« on: February 13, 2007, 07:02:43 pm »

hello,

i would like to isolate a post production style control room from an office that shares a common wall.

would sheet block on one side of the wall with a layer of 5/8ths added,

do better then,

rc-8, insulation and  a layer of 5/8ths?

would either of these be an effective treatment if moderate to medium loud volumes are in play?

thanks in advance.
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R. Steele

franman

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Re: isolation / common walls
« Reply #1 on: February 14, 2007, 09:36:53 pm »

simple question... not so simple answer..

Take the existing common wall..
1. What is the construction?? Single 5/8 GB on each side??
2. Doubling the mass of the wall will offer approximately 6dB improvement in broadband Sound Transmission Loss... of course no where near that amount at lowest 2 or 3 octaves.
3. Improvement of existing GB walls with sheet block is not something we typically recommend. First, the mass of the sheetblock is typical less than 1 layer of 1/2 or 5/8 GB.. about half! The limp mass effect of the sheetblock is lost when it is added to, or sandwiched between other rigid laminations... so typically we resort to more standard rigid building materials that are more readily available, weight more and are easier to install (think MDF and another layer of GB.. that will add some mass!!).
4. To make a significant improvement over doubling the mass the first time, you have to double it again!! FOUR layers on each side?? Probably not gonna happen.

5. RC channel is great stuff!! It has to be installed and used properly:  FIRST, it is meant to be used over the stud bay or airspace to get the best improvement in LF transmission loss.. if used over an existing layer of GB it can actually decrease the LF transmission loss over the addition of a 5/8" sheet directly to the existing wall (is that clear??)..
SECOND, it has a maximum load capacity above which it is no longer "resilient".. typically for 1/2" RC-1 (USG) this is 2 layers of 5/8" Gyp Bd on a wall or ceiling (pressing it on the ceiling).
THIRD, it should be installed with the free leg facing up and run horizontally across the open studs, insulate the wall and add the two layers of 5/8".. This type of installation can actually offer up to a 5dB improvement in LF Transmission loss over the same construction without RC channel..

so what's best for you??
1. What's the exisiting common wall? 1 layer of 5/8 on each side of stud? (Return to top and cycle indefinitely!!)>>>> Twisted Evil
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Francis Manzella - President, FM Design Ltd.
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i dig music

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Re: isolation / common walls
« Reply #2 on: February 15, 2007, 09:05:59 am »

thanks Francis,

thats some great info.
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R. Steele

J.F.Oros

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Re: isolation / common walls
« Reply #3 on: February 15, 2007, 05:13:08 pm »

You also have to take in consideration the flanking paths, because the sound is leaving your room not only by air and direct exciting the walls, but also through auxiliary paths, the strongest being from the direct contact of the speakers/stands to the floor.

If this connection is not mechanically decoupled (by vibration insulators with a verry low resonance frequency) then a lot of speaker LF energy is transmited verry efficiently to the floor and from there to the entire building structure, making it much harder to stop the leakage to the other rooms, even if you reinforce the walls.

If the problem comes from the exterior and you are trying to insulate the interior from the outside noises, this is much harder to do, most of the times requiring a full floating room to be constructed inside.
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[ Flaviu Oros - acoustics engineer ]
[ JF Studio Design - Romania ]
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