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Author Topic: isolation quandary  (Read 1743 times)

Yannick Willox

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isolation quandary
« on: January 12, 2007, 12:07:53 PM »


We are embarking in a construction project, where me and my wife will build a private house with some professional parts.
We are both pianists (hence a rehearsal room) and I have a small mobile recording company.

The big studio would be below ground level, the small studio would be ground level , next to the piano room, but separated by a corridor of 1.5m. For now let's assume all outside walls and floors are 25 cm concrete, inner walls 15cm and inner floors 20cm concrete + additional layer of concrete/wood/insulation whatever...
(Cross section below)

Some important points :
1. piano is not VERY isolated from the house (ground floor) - by the layout of the house and because we don't feel it to be necessary. However, if we can get adequate isolation to the upper level (bedrooms) that would be great. I was thinking hanging a ceiling under the concrete floor and decoupling the concrete upper floor from the side walls (during construction !), reducing flanking noise upstairs. This way I wouldn't make the available space smaller by adding walls.

2. the small studio : it is not critical to get great isolation, but I would want to build a box in a box anyway, because in the latest plan it is built above the big studio, so the concrete floor is suspended in air - in a previous plan it was laying in the ground, so it would resonate less.

Q: do I put in a floating floor ? Or will this create a triple leaf with :

3. The big studio underground. Should be able to be used 24/24. People/children will have to sleep 2 stories up.
I assume flanking noise through the floor and up will be no problem !
I intend to put inner walls&ceiling, decoupled from the outer structure to minimise flanking noise through the walls.
Should I make a box with ceiling, or resilient walls and ceiling ?

Does anyone have some brilliant insight ?
Where could be the weak link, which ceiling/wall should I take most care of ?

If there is a triple leaf effect between the two studios, which is more important : the floating floor in the upper studio or the decoupled ceiling or box-in-a-box in the lower studio ?

Your advice is appreciated - who knows, maybe I'll need someone to consult me on the acoustics ...
Yannick Willox
Acoustic Recording Service


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Re: isolation quandary
« Reply #1 on: January 12, 2007, 10:52:39 PM »


I realize your concern, but if the isolation of the piano is the main concern, I don't think structurally isolated construction is necessary... Yes, I know that the piano, can be quite a loud instrument, but the amount of very low frequency is not heavy and is not constant, like LF bass and drums in pop music.

The mixing studio would potentially have more impact on the structure, even though the piano is sitting on a structural slab.


#1... get a piano dolly with rubber wheels...this will help with structural coupling to the slab and is relatively inexpensive compared to decoupling slabs properly.

#2. I would suggest that you suspend a ceiling above the mixing/mastering room downstairs. You can investigate resiliently suspended this ceiling with springs and a frame system... A captured air space with at least two layers of drywall and an insulated cavity will make a great improvement in the up to down isolation... this could be the top of your box inside a box, or you could span the ceiling framing from top of wall to top of wall depending on the lengthof the spans involved.

#3. when it comes to the resilient mounting of walls, floors and ceilings we generally feel that structural decoupling is best used when the entire inner box is decoupled. This means everything is built on top of a properly floated floor. Properly is the key word here... We see MANY incorrectly floated floors every year.. There is some engineering required to determine live and dead loads, amount and spacing (and rating) of isolators, and deflection of the isolators which determines what the resonant frequency of the isolation system will be.... this is where hiring a professional is helpful...

If you are building (down stairs) on slab on grade, I would most likely suggest building heavy inner walls that don't connect to the slab above and a resilient ceiling... skip the floor. It's hard to get right, eats up ceiling height and you will do better to concentrate on the resiliently suspended ceiling IMHO.

#4..what type of playback monitors are you using in your studio rooms... I ask to determine what amount of low frequency you will be dealing with.

concentrate on mass first... airspace is essential to any multi boundary system as well.. Dampen all interstitial airspaces with generous amounts of insulation... AND.. SEAL ALL HOLES as these are the most common flanking paths in non-professional designs and construction in our experience...

Hope this helps.. more specific questions will get more specific answers...

Francis Manzella - President, FM Design Ltd.
                 - Managing Director, Griffin Audio

Yannick Willox

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Re: isolation quandary
« Reply #2 on: January 13, 2007, 05:42:11 AM »

Thanks. Now I have more questions of course.

1/ The piano has been on sylomer pads since a while, and will be. It's a floating piano  Cool The sylomer pads are 10cm circles, and I found 10cm teflon gliding pads which go underneath. So basically I have a gliding floating piano.

Q1/ do you mean structural decoupling is only for LF isolation ?

2/ OK. The spans in the cellar will be 6-7m. The spans on the ground floor 4-5m.

3/ Is this because the floor gets more mass which lowers the resonant frequency ? Or mainly because the airgaps are bigger than with resilient walls ? (our current floating floor was calculated by a professional btw)

3b/ a heavy inner wall seems more practical indeed, if it doesn't tip over. Do we fill the air gap between two heavy walls ? Is the gap as important as with light walls ?

4/ Monitors go down to 45Hz. But the small studio will have one sub to 18Hz and the big studio (underground) two. On the other hand 90% of our work is classical music. The rest is jazz. We work at an average level of 83-85 dB.

Q: floating floor on a concrete slab above suspended ceiling: is this a triple leaf ? Or not because the three "floors" are so different ? (wooden floor/concrete slab/drywall ceiling)
Yannick Willox
Acoustic Recording Service
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