Elastic or rigid room in room walls

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Elastic or rigid room in room walls

Postby dragos strat » Fri Oct 18, 2013 7:40 am

Hi everybody,

these days I end the soundproof work at my mini studio/rehearsal room. The space is located in the basement of a 2 store building made from bricks and supporting-on-walls concrete floors. The building is old (from the fifties). The basement space (former cellar) its small - 12 square meters. it had a small window witch right now is transformed in a air evac system with sound filters on in and out vent pipes. all ventilation elements are inside of a niche made with the same walls materials and weight.

i made a structure room in room type with a total amount of 22 cm space between walls and 32 cm at the ceiling.

My structure is from outside to inside:

Walls: 2,5 cm hard foam (90 kg/m3) - 5cm mineral wool (40kg/m3) - 5 cm air space- 10cm same mineral wool - vertical steel slabs (standard for gypsum frame) from 30 cm to 30 cm - 4 acoustic gypsum boards (11,6 kg mp) with 3 sheets of roofing felt (4 kg square meter each) between them. total weight is about 60 kg per square meter

Ceiling: had the same structure but the space to the structural ceiling is 32 cm, I use 10 cm layers of mineral wool, and I combined wood slabs with steel slabs for rigidity. (its a dorm above)...

Floor: ply 2cm - 2 sheets of gypsum boards - 2 sheets of 1cm ply on rubber I also gained here 60 kg/ square meter

Of course nothing touches the building, I added two doors plated with 2 gypsum sheets

Right now all the weight of the ceiling rests on the walls (the steel slabs are elastic and cannot sustain all the weight), the walls are kinda elastic, when I press them in the middle they move maximum 5 -6 mm.

My question is, I will gain better isolation of low frequencies adding on every wall a rectangular pipe frame 5cm x 3cm x 3mm attached on the wall with elastic adhesive, and many screws? eventually I could fill the pipes with sand for greater weight. The frames will have reinforcement pipes inside for added rigidity.

I cannot find anywhere on the net this info or this procedure, its my solution regarding resonance. My thinking is - if I reinforce the wall I will increase rigidity and it will lower the resonance frequency.

What do you think about this solution?
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Re: Elastic or rigid room in room walls

Postby bert stoltenborg » Fri Oct 18, 2013 9:59 am

If you make a construction stiffer you raise resonance frequency and Q, what in general is not good for isolation of music.
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Re: Elastic or rigid room in room walls

Postby Scott R. Foster » Fri Oct 18, 2013 11:23 am

Mass is your friend - but sand filling partitions has always struck me as overly complex - and the thought someday someone might drill a hole and "drain" the wall sounds like a very high potential for an "oh-shit" episode. Wouldn't it be easier to lay on additional sheets of drywall until you reach your mass goal?
SRF
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Re: Elastic or rigid room in room walls

Postby dragos strat » Fri Oct 18, 2013 11:24 am

bert stoltenborg wrote:If you make a construction stiffer you raise resonance frequency and Q, what in general is not good for isolation of music.


So its better for low frequencies isolation to have more flexible than rigid walls, thanks. Hopefully tomorrow I'll take my chances and test the room with a bass drum and a low tom. Wish me luck, this was the 4th project on this room, the other ones was a failure because I haven't decoupled the walls and ceiling ...
Last edited by dragos strat on Fri Oct 18, 2013 11:39 am, edited 1 time in total.
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Re: Elastic or rigid room in room walls

Postby dragos strat » Fri Oct 18, 2013 11:31 am

Scott R. Foster wrote:Mass is your friend - but sand filling partitions has always struck me as overly complex - and the thought someday someone might drill a hole and "drain" the wall sounds like a very high potential for an "oh-shit" episode. Wouldn't it be easier to lay on additional sheets of drywall until you reach your mass goal?


Sand filling just the interior of the pipes, not the hole partition. Sorry for my bad explanations.. :D. About the mass goal - I think I achieved already with 60 kg / square meter. To have a slight difference in the isolation I should go above 100 kg per square meter and in my 10 square meter of remaining space would be almost impossible to have 3 musicians rehearsal there...

I just need to find out if elasticity or rigidity of the walls would make a change in the isolation (interested only in changes (even small) in better isolation of low frequencies :D )
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Re: Elastic or rigid room in room walls

Postby Bob » Fri Oct 18, 2013 4:35 pm

The rule of thumb is that drywall is the cheapest way to add mass.
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Re: Elastic or rigid room in room walls

Postby bert stoltenborg » Fri Oct 18, 2013 8:13 pm

How is the floor of the store above you constructed and what is happening there?
Normally you cannot have a rehearsal room in a building without eventually getting killed by annoyed neighbours.
:D
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Re: Elastic or rigid room in room walls

Postby dragos strat » Wed Oct 23, 2013 2:16 pm

bert stoltenborg wrote:How is the floor of the store above you constructed and what is happening there?
Normally you cannot have a rehearsal room in a building without eventually getting killed by annoyed neighbours.
:D


Back!

This days I'm working on room treatment, I do it myself - already injured a finger in the process off cutting a wood :( ... Still wasn't able to test the isolation, my drummer friend has a bad cold. Im waiting anxious to see if my 2800 euro isolation is working...

To answer your question, the floor of the room above its made of concrete panels with reinforcing bars resting on brick walls.
When my worker was cutting a door with jig saw inside room in room, with only the interior room door closed (but not sealed), I put my ear on upstairs wall that it has direct connection with a structural wall from my space and I could hear the jig saw but a faint noise, no vibration, I could hear the medium and the low spectrum of the jig saw.

I measured the noise levels few months ago with a professional frequency db meter (from faculty of civil engineering) and my result was:
(Rehearsal room was isolated with 4 layer of gypsum board - steel slabs direct connected to structural wall and air space of 9 cm filed with fiberglass wool) The floor was disconnected from the walls resting on hard rockwool 90 kg square meter ) - two doors

Pleas see attached:
measurment-levels.jpg
Measurement levels
(220.4 KiB) Not downloaded yet


At that time the levels was way above the legal regulations from my country witch are +5 db above the "local silence". I had a global 12 dbs plus..
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Re: Elastic or rigid room in room walls

Postby Yannick » Sat Oct 26, 2013 1:58 pm

bert stoltenborg wrote:If you make a construction stiffer you raise resonance frequency and Q, what in general is not good for isolation of music.


I find this advice confusing, and most often disturbing.
I have had the very same advice in the past, and did not follow it, for several reasons:

1. even if the walls are stiffer and the resonant frequency is higher, overall inherent TL in a heavy wall partition is anyway much higher.
2. I have test data of the national research council Canada, clearly showing that 90mm+115mmair+ 90 mm conrete block walls (quite thin!) have an overall STC of 77 dB (and around 48 dB TL at 80Hz).
3. A single leaf of Ytong 240mm or lime-sandstone (Silka, 150 mm) already has 30 dB of TL at 80Hz, more or about the same than a standard brick wall + resilient clips + 2 layers of gypsum board
4. even a staggered leaf wall with 2x 2 layers with green glue in between has TL at 80Hz of only around 30 dB.
5. 80 Hz is where a lot of energy is, even when doing just classical music.

So, even with inherently stiffer walls, and possibly worse coincident dips, the sheer mass of a two leaf concrete block, or in my case Silka/Ytong almost completely eliminates bass transmission.
It is quite easy to have 20dB more TL in such a heavy assembly, even with massively smaller (around 100mm opposed to 200mm ?) air gaps.

In my mind, a flexible wall must inherently pass through LF much more easily, as it will act as a giant drum skin.

The weakest link in my studio (after the door of course) must be the ceiling, but to the contrary of regular advice, I made the wooden structure as rigid as possible. What I wanted to avoid was a resonant structure that actually resonates in the neighbourhood of the 300mm air gap (half full with rockwool). The only thing I can hear extremely faintly (when I have complete silence) is impact noise on the concrete floor above my studio ceiling (= single leaf only in that special case).
What you can never hear upstairs is bass, bass drum etc.
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Re: Elastic or rigid room in room walls

Postby bert stoltenborg » Sun Oct 27, 2013 1:15 am

You're confusing things, dude.
Read your stuff and come back.
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Re: Elastic or rigid room in room walls

Postby Yannick » Sun Oct 27, 2013 8:13 am

Bert,

I looked long and hard years ago. I never found measurement data for sheetrock in front of a brik wall, not touching.
Every measurement I see of sheetrock attached (even with resilient channels) to a heavy wall, TL is actually worse at LF (below 100 Hz) than just the wall.

Maybe if you increase the airgap enough, our really decouple from the wall ? But as I said, please show me to some data.
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Re: Elastic or rigid room in room walls

Postby bert stoltenborg » Sun Oct 27, 2013 10:17 am

Hoi Yannick,

See for example the information Vermeir and Thoen of the KU Leuven retrieved in 1995 for Nevima, reports 3762, 3787, 3786, 3785 3766, 3780, 3764.
Here a 10 cm kalkzandsteen (limestone) wall is measured untreated and with several constructions in front of it.
RA(popmusic) for the wall is 36 dB, and with the supporting constructions improves to 57 dB.

A rehearsing band does 110-120 dB(pop), minus 57 leaves a 53-63 of noise. In Holland 25 dB(pop) is allowed inside a living space.

From memory I think even Paul Woodlock said his construction didn't really allow drumming, and his construction was ahead of what the OP is describing.
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Re: Elastic or rigid room in room walls

Postby Bob » Sun Oct 27, 2013 11:49 am

"Noise Control In Buildings" by Cyril M. Harris, has several pages of 63hz to 4000hz measurements for {4", 6", 8"} x {solid Concrete, not filled Concrete Block, filled Concrete Block} walls.

Wall #1a: [6" (140mm) 75%-solid concrete block]: 63hz 35dB

Wall #1b: [6" (140mm) 75%-solid concrete block, 1.5" (38mm) wood furring, 1.5" (38mm) fiberglass batts, 0.5" (13mm) gypsum board]: 63hz 32dB

Wall #1c: [0.5" (13mm) gypsum board, 1.5" (38mm) fiberglass batts, resilient channels, 6" (140mm) [not filled] concrete block, resilient channels, 1.5" (38mm) fiberglass batts, 0.5" (13mm) gypsum board]: 63hz 28dB

Wall #1d: [0.5" (13mm) gypsum board, 1.6" (40mm) fiberglass batts, 1.6" (40mm) steel studs, 6" (140mm) [not filled] concrete block, 1.6" (40mm) steel studs, 1.6" (40mm) fiberglass batts, 0.5" (13mm) gypsum board]: 63hz 23dB

Wall #2a: [8" (190mm) [not filled] concrete block, 5/8" (16mm) gypsum board ]: 63hz 36dB

Wall #2b: [5/8" (16mm) gypsum board, 3" (75mm) Z-channels, 8" (190mm) [not filled] concrete block, 2.5" (65mm) steel studs, 5/8" (16mm) gypsum board ]: 63hz 25dB

Wall #3: [4" (90mm) concrete block, 2.4" (60mm) air, 2.5"(65mm) rigid fiberglass, 4"(90mm) concrete block, 5/8" (16mm) gypsum board]: 63hz 41dB



IRC concrete block ir586.pdf
compares single concrete block, against a Wall#3 style, and finds that LF (63hz to 100hz) transmission loss goes up (good) in every case they tried Figure 11, and last pages of Appendix A2.
Presumably the resonance frequency of Wall#3 style [block,insulation,block] construction is lower than 63 hz.
Last edited by Bob on Sun Oct 27, 2013 12:26 pm, edited 2 times in total.
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Re: Elastic or rigid room in room walls

Postby Bob » Sun Oct 27, 2013 12:15 pm

bert stoltenborg wrote:If you make a construction stiffer you raise resonance frequency and Q, what in general is not good for isolation of music.


Yannick wrote:In my mind, a flexible wall must inherently pass through LF much more easily, as it will act as a giant drum skin.


IRC ir761 walls.pdf (Canada)
From the few examples I looked at for gypsum board walls [gypsum, wood studs&insulation, gypsum], moving from studs every 610mm (24") to 406mm (16"), i.e. making the wall stiffer, had no effect at LF (63hz to 80hz), but lowered STC (average of all frequencies).
i.e. stiffer lowers STC (bad). Flexible raises STC (good).
Although rather than stiffness, the lowering of flanking and increasing of cavity size (not depth but width, and relative percentage area), might be factors too.



IRC ctu13e Concrete Block Walls.pdf
Figure 2, compares bare blocks, against 13-mm resilient channels, against 75mm resilient z-bars,
and LF (63hz to 100hz) transmission loss goes down with the channels,
which they attribute solely to mass-air-mass resonance.
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Re: Elastic or rigid room in room walls

Postby Yannick » Mon Oct 28, 2013 4:14 pm

Bob, those were the documents I looked into quite a while ago.
They seem to confirm that TL (and even more so at low frequencies) is way superior for a block-airgap-block wall, compared to a double gypsum construction or gypsum-air-block.

In this case, as concrete blocks surely are stiffer than gypsum board, the resoning: higher resonant frequency = worse TL does not fly.
TL of these double heavy walls is much better, and the walls are much stiffer, but they are not 10x more heavy ?

So something else must be going on ?

Five years ago, I consulted Eric just briefly, and he gave me the exact same advice (AGAINST using heavy blocks - air gap - cellular conrete blocks). He preferred in my case to use gypsum walls in front of the CC blocks. He used the same argumentation: less stiff, more lossy, lower resonant freq, coincident dip avoided.

I simply think this reasoning is not correct for really heavy, thick double walls.
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Re: Elastic or rigid room in room walls

Postby bert stoltenborg » Mon Oct 28, 2013 4:22 pm

This is getting a bit silly.
Don't you understand what you are saying, or don't you want to understand?
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Re: Elastic or rigid room in room walls

Postby Yannick » Mon Oct 28, 2013 9:57 pm

I do not have access to the reports you mentioned.
So I do not understand what you are saying, except the silly part and if I understand what I am saying, which isn't sayingme much.

Question: do you consider a concrete block wall as a stiff construction, or elastic ?
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Re: Elastic or rigid room in room walls

Postby dragos strat » Wed Oct 30, 2013 8:21 am

Yannick wrote:Bob, those were the documents I looked into quite a while ago.
They seem to confirm that TL (and even more so at low frequencies) is way superior for a block-airgap-block wall, compared to a double gypsum construction or gypsum-air-block.

In this case, as concrete blocks surely are stiffer than gypsum board, the resoning: higher resonant frequency = worse TL does not fly.
TL of these double heavy walls is much better, and the walls are much stiffer, but they are not 10x more heavy ?

So something else must be going on ?

Five years ago, I consulted Eric just briefly, and he gave me the exact same advice (AGAINST using heavy blocks - air gap - cellular conrete blocks). He preferred in my case to use gypsum walls in front of the CC blocks. He used the same argumentation: less stiff, more lossy, lower resonant freq, coincident dip avoided.

I simply think this reasoning is not correct for really heavy, thick double walls.


For me, a less educated in acoustics and sound isolation (I'm just a musician) its logical to make an analogy with guitar string or drum shell. Higher you tune the string (drum shell) it will resonate at a higher freq. Simple as this. :D So instead of a wall if we had a blanket with the 60kg + / square meter mounted on the slabs it will isolate better (Im thinking here at lead )

By the way of lead. I found a wonder product sold here in Romania. its a membrane and in the specs they say it isolate better then lead at the same thickness. 11 db at 125 Hz jut by it self (not included in a system) . Should I believe this numbers? If I mounted it as a final 9nside in room layer of my system witch is already 60 kg /square meter I will gain even 6 dbs at 125 hz?

http://www.heavyfoam.com/blocktec-50.html

I made the test yesterday with a drummer, a bass drum and low tom. The bass drum (a big 24" model ) was hit insane hard and it was plane empty inside (a lot of resonances). In the room above the rehearsal space, I could hear some low freq but I couldn't figure if was 30 or more dbs... I asked the old lady ho lives there if she could hear the drums but she is a little deaf and she couldn't tell if there was some low freq leaks from my place. That said, it was no vibration in the wall or the floor it was just airborne sound coming from below. I'm content but not fully. The old lady it very old and now I just pray to stay longer in the apartment. If she'll rent the room or move, new maybe younger neighbors with good ears will come and the problem will start again as in the past the room above was rented to a young couple from the country side used with complete silence :(.

I this case If I should believe the dbs isolated by Blocktec, shoud be complete silence above me, but I learned that in sound isolation things are counter intuitive... (100 kg/sq meter wall will not double the isolation of a 50 kg/sq meter wall - I steel make efforts not to use same intuition an logic of "normal" things"
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Re: Elastic or rigid room in room walls

Postby bert stoltenborg » Wed Oct 30, 2013 10:36 am

It's just adding mass, so your 60 kg/m^2 will become 67 kg.
You'll not notice that as an improvement of noise reduction.
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Re: Elastic or rigid room in room walls

Postby Ido » Wed Jul 29, 2015 12:22 am

Yannick wrote:....

Five years ago, I consulted Eric just briefly, and he gave me the exact same advice (AGAINST using heavy blocks - air gap - cellular conrete blocks). He preferred in my case to use gypsum walls in front of the CC blocks. He used the same argumentation: less stiff, more lossy, lower resonant freq, coincident dip avoided.

I simply think this reasoning is not correct for really heavy, thick double walls.


Cant sleep, stumbled on this, think i understand the unclarity, its specifically about those cc lightweight blocks, if you would have told the master the second wall would be heavy not airy blocks he would have said something else...
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