2 Basic Things

Fieryjack · Post by **Fieryjack** » Wed Jun 25, 2003 11:20 am

Hello:

Here are a couple embarassingly basic questions:

Any help is appreciated!

1) When constructing a basic room (before treatment), which kind of insulation do I put in-between the studs? The Owens Corning 703 (firm stuff) or the regular fluffy stuff?

2) Is there a cheaper U.S. equivalent of Auralexs' "Sheetblock"? I was a little surprised at how expensive this is ($360 a roll). Would another less expensive brand give me similar fire retardant/sound proofing qualities?

Thanks in advance. jeff

knightfly · Post by **knightfly** » Wed Jun 25, 2003 6:57 pm

1 - The 3 pcf 703 (or rockwool) will give a few dB better TL at lower frequencies than the fluffy stuff, but probably a few dB WORSE TL at upper mids/highs. Generally, if you can bias this performance to LOWER frequencies the Music Transmission Class performance will be more balanced.

2. The SheetBlok stuff really is un-believably expensive - I'm still waiting to be convinced that it's worth that much. Maybe if Eric is still around he would be willing to help both of us understand its value... Steve

Eric_Desart · Post by **Eric_Desart** » Wed Jun 25, 2003 8:28 pm

knightfly wrote:2. The SheetBlok stuff really is un-believably expensive - I'm still waiting to be convinced that it's worth that much. Maybe if Eric is still around he would be willing to help both of us understand its value... Steve

No it isn't.

Will explain more in-depth later.
This is typical acoustics as magic.
Just substitute the sheetblock by another layer of gupsumboard and the difference in TL can hardly be measured.

Never noticed that one finds technical TL data for sheetblock or comparable alone (measured as a freehanging object)? Somehow this should suggest that those values could be added to the wall.
Also never noticed that you NEVER will find a comparative measurement between a wall with sheetblock and a EQUAL good drywall where the sheetblock is substituted by another layer of drywall?

It has it's effects but in combination with other drywall layers, any positive effect is hardly measurable.

Give the same amount or even less to drywall layers and your wall be better. The most important is cavity width and number of layers.
It's good to add an addition thin layer 3/8" or something to increase internal damping and improve the coincidence.
But the MAIN factor remains Mass-Spring-Mass.

Conclusion: for TL of drywall it's very bad added value/Price.

Note in the ousite studio professional world (note that drywall for studio is only fraction of a % of the market) those mass loaded layers aren't considered as a valid option. And you can be sure that banks (and thousands of other applications) don't mind paying more to increase privacy by increased TL.

Best regards
Eric

Fieryjack · Post by **Fieryjack** » Thu Jun 26, 2003 1:52 am

Eric/Knightfly:

I plan to have 1" x 4" pine panelling in my live area...originally, I was going to have the sheetblock sandwiched inbetween the substrate (plywood) and the panelling....

If I am not using drywall (i.e. I cannot attach the panelling to drywall), is there an alternative to sheetblock? Another layer of what?

Thanks again.

p.s. is Gypsum board the same thing as drywall?

Eric_Desart · Post by **Eric_Desart** » Thu Jun 26, 2003 3:06 am

Fieryjack,

Gypsum board, Plasterboard, Drywall, sheetrock = all the same, name depends on regional customs.

Can't you use gypsum board or an alternative behind the plywool.

What about particleboard?

Basically gypsum board has better properties than wood.
You can of course use sheetblock, but as you say = expensive.
You gave a price per roll. How much is on a roll.
A roll is a bit a subjective unit to calculate with.

Regards
Eric

Fieryjack · Post by **Fieryjack** » Thu Jun 26, 2003 4:24 am

Basically gypsum board has better properties than wood.

.

Eric, I am assuming you mean STL/soundproofing properties....what about Acoustic properties? Is sheetrock often used in live rooms (sorry if question is dumb, once again)?

I would LOVE to use sheetrock because it is so cheap....but always thought wood would sound warmer or something. FYI, tracking multi instruments incl. drums, bass, acoustic instruments, etc. What do you think?

Jeff

Eric_Desart · Post by **Eric_Desart** » Thu Jun 26, 2003 4:47 am

Again a dangerous question?

What is sounding good?

Wood, if profiled a bit, can have a bit scatering of sound in highs (but in fact thats minor).
This typical wood sound is mostly caused by wood which can freely vibrate and has its specific resonances.

But whatever: when it adds to the sound it's coloration.
Is that good? Up to you to decide.

Slats in Helmholtz mainly scatter and reflects. While also mids and highs it doesn't necessarily add to the coloration (mainly reflection, scattering and absorption).

STRICTLY PERSONAL, when something sounds like wood I restart until it doesn't anymore. The idea is to hear music, not wood.

You're fun.
You ask if drywall is the same as gypsum board and than starts talking yourself about sheetrock.

Personally I think sheetrock is very good. It's often easier to correct nothing than to remove something (refering to this minor diffraction scattering).

And for insulation the standard materials are still the best and the cheapest (sheetrock, concrete, bricks, fiberglass, rockwool, wood for slats, whatever)

Regards
Eric

Fieryjack · Post by **Fieryjack** » Thu Jun 26, 2003 5:07 am

Eric,

Thanks again for the very thorough and useful response. I'm getting there....

So there are some very good arguments for using sheetrock, a primary one being that it doesn't color the sound like wood does.

Last question (and again, likely a silly one at that!): If you're starting w/a room that has sheetrock walls, how do you attach acoustic treatment (i.e. slats, etc.)? Would acoustic treatment need to be free-standing?

Thks again.

knightfly · Post by **knightfly** » Thu Jun 26, 2003 8:28 am

Eric, thanks for confirming my suspicions on the Sheet Blok - The pricing I saw, makes sheet blok about 8 times as expensive as the same area in sheet rock. About the only (maybe) valid use I could see for the stuff is if you need a mass layer without the thickness of sheet rock - even then, it's so expensive that maybe sheets of GOLD would be cheaper, and more mass :=)

As to the chaos of multiple names for same thing, I think this should be the subject of the next world standards meetings - a universal name for this material - I believe "Sheet Rock" is actually a trade name of US Gypsum, Gypsum Board is generic, Wall Board is generic, Gyp-Rock may be a trade name, Dry Wall is generic, and plaster board is also generic. I also find myself trying to figure out which of the many names I'll use when describing a wall construction...

There may be a few other names for it, but it's all just a couple of sheets of fancy paper with some white junk squeezed in between, and it's just a really good thing (in this case) that the general building material manufacturers don't yet know how good a bargain the stuff is for studio building, or it would suddenly cost $25 per sheet

FJ, various acoustic treatments can be mounted to existing walls (preferably to studs) or they can be free-standing in some cases. Absorptive treatments, such as cloth-covered 703, can be either hung loosely or mounted to the wall - there are test criteria, one of which mounts the material off the wall by about 16" (400 mm) and others which test it placed against the wall, etc - in the case of 703, you get better low frequency absorption by spacing it off the wall (mainly in the case of perpendicular incidence, grazing incidence changes many materials' performance)

For things like slat absorbers, they can be mounted to framing studs through drywall (although screws thru sound proofing layers decrease the TL) - Doing this would negate the need for a back on the slat absorber, as long as you sealed the side frames to the wall... Steve

AndrewMc · Post by **AndrewMc** » Thu Jun 26, 2003 8:52 am

Eric - more informative & excellent posts - I'm confident that everybody here is very appreciative of your participation (so you are going to be a moderator right

)

A question based on your posts in this thread. I think i know the answer but it'd be great if it was cleared up 100% in my mind.

- In a mass-spring-mass wall - the insulation does not reduce the effective size of the spring (air space) - Is that correct?

- Also - if you were building such a wall - would you put regular non dense insulation in the air space, or would you use dense 703 type insulation?

Thanks!

Regarding the sheetblok - that stuff is crazy prices. I'm planning to use a small amount but just on doors. Mineral loaded roofing felt is approx 1lb / sq ft (1 roll is hard to lift) - it's Class A fire rated, and only costs about 13 cents / sqft - very cheap & freely available at Home Depot. I read on the net a studio design where they used it.

Eric_Desart · Post by **Eric_Desart** » Thu Jun 26, 2003 9:28 am

Andrew,
Many thanks for your kind words.

AndrewMc wrote: 1) - In a mass-spring-mass wall - the insulation does not reduce the effective size of the spring (air space) - Is that correct?

2) - Also - if you were building such a wall - would you put regular non dense insulation in the air space, or would you use dense 703 type insulation?

3) Mineral loaded roofing felt is approx 1lb / sq ft (1 roll is hard to lift) - it's Class A fire rated, and only costs about 13 cents / sqft - very cheap &

1) No if you use wool or comparable. Gasflow resitance is that low that it has minor effect on MSM but huge effect on damping.
Yes if you use closed cell thermal insulation foam as polystyreen, hardfoam polyurethan etc. Those materials destruct properties for the very reason you mention.

2) I've seen steve has some fixed rules for that. For me after 25 years it's not yet clear. I think that 702 and 703 is good. I'm not sure I agree with Steve on the higher density for better low frequent absorption.
Full cavity filling is good (is often mentioned otherwise).
Very interesting are those PAC measurements.
http://www.pac-intl.com/tests_wl_wood.html#st
Forget about the 160 Hz band (something happened there).
Also the RSIC dampers, while certainly good I have the suspicion that this is only secundary to the good results of those walls.

What strikes me (most will not notice it) is that they use R19 blanket which is pessed together in those walls with ca 30 mm (1.2").
I have the feeling that this works as a damping on the wall. Never tested this, but this intreges me for over a year now.
I have the feeling that some good things are used their which they point to RSIC, but I think that other things contribute:

1) this wool acting as a damper.
2) One sided relative close wooden studs surpressing low bending waves.
3) Increased cavity width by the RSIC.
4) The RSIC which must have a lower resonance frequency than RC.

I think 1) and 2) are important points here.
Lots of modern roofing types at least as good and often better than mass loaded vinyl.
Disadvantage is temperature reach.
At room temperature roofing is perfect.
At very cold temperatures mass loaded vynil is better.
The properties of those materials very with temperature and have a rather small piek range in function of internal damping..

Best regards
Eric

knightfly · Post by **knightfly** » Thu Jun 26, 2003 11:10 am

Eric, I'm glad you questioned my statements on insulation densitiy - the good news is, I found the page in USG's construction manual where I read it - the BAD news is, I was apparently half asleep (the head half, not the feet half) when I read it, because it says JUST THE OPPOSITE of what I thought it said... Here 'tiz, check for yourself...

http://www.usg.com/Design_Solutions/2_3 ... onperf.asp

And now, I must stand at the chalk board and write...

I must read more carefully, I must read more carefully, I must read more carefully, I must read more carefully, I must read more carefully, I must read more carefully, I must read more carefully, I must read more carefully, I must read more carefully, I must read more carefully, I must read more carefully, I must read more carefully, I must read more carefully, I must read more carefully, I must read more carefully, I must read more carefully, I must read more carefully...

Hey, at least I was right on the PREFERRED density... :=)

Eric, if the info on USG's site is valid, maybe a wall with INTENTIONALLY reduced insulation density would compensate for the STC vs. MTC ratings, and actually be BETTER for music - if so, compressing R19 batts in a 3.5" steel stud partition might work well???

Just speculating... Steve

Eric_Desart · Post by **Eric_Desart** » Thu Jun 26, 2003 8:02 pm

Hello Steve,

I will be blocked for probably a week or so, that I don't find time to go in depth.

So I'm not going to search now for the exact links (time consuming)

Stan Roller (name?), designer of the MTC, somewhere has an article on the USG site where he states that certain types of rockwool with somewhat higher density are better than the standard fluffy stuff. He's right. So the really light stuff isn't good.
Note that Stann Roller refers to rock wool which belongs to USG (nowhere mentioned). So don't look at the brand.

I believe the BBC studies are the best to base yourself on. Problem they don't mention density.
But I assume (I have lots of internal documents of BBC) that they use cavity filling in fiberglass of around 40 kg which should equal OC 702.
This about fits my experience.
For one or another reason fiberglass gives better results than rock wool.
The BBC R&D, in function of studio things must be one of the best in the word.

However those PAC measurements really intrege me, but I can't give a conclusive answer.
My instinct and knowledge tells me that a few clever guys, tried some unconvential techniques here to boost the insulation (than assigning the result to the RSIC thing).

I really should like to know the density of this R19 stuff, in order to get an idea about the compression.

If you look in the link section of the Yahoo group. I collected lots of interesting links there. Maybe check them, you can use them here as well.

So as far my instinct + numerous measurements I made goes. I should opt for fiberglass of 32 to 40 kg/m3 (that's about OC 702), with full cavity filling. But somehow I should like to further investigate the original PAC approach which fits a logical physical approach. (Never saw that anywhere else, and they don't mention it. You just must carefully read the official reports to notice this).
Don't ask exactly why, but the BBC studies empirically show better low frequency results for fiberglass than rock wool. And they really are good those guys.

So I have no conclusive answer. But I think that 703 is already on the (too?) heavy side.

Best regards
Eric

Just a few links:
I hope they work:
http://www.eurima.org/downloads/Fact_Sh ... illing.pdf
http://www.usg.com/Design_Solutions/2_3 ... onperf.asp
Sorry just saw: this is the one you mentioned: The author of this article is the designer of the MTC standard (never became official). OITC (official standard) is better = also designed by ex-USG guy.
http://www.nrc.ca/irc/cbd/cbd239e.html

Sen · Post by **Sen** » Thu Jun 26, 2003 10:30 pm

knightfly wrote:About the only (maybe) valid use I could see for the stuff is if you need a mass layer without the thickness of sheet rock - even then, it's so expensive that maybe sheets of GOLD would be cheaper, and more mass :=)

Sen · Post by **Sen** » Thu Jun 26, 2003 10:34 pm

AndrewMc wrote: Regarding the sheetblok - that stuff is crazy prices. I'm planning to use a small amount but just on doors. .

I just checked the price of lead at a local plumbing supplier....
$145 AUD (about $80 US) for 3 metres of 60 cm wide lead sheet (comes in a roll)
I know that's not cheap either and not sure how it compares with sheetblock, but I imagine it would be much more massive.....If I ever build a studio I'll put lead on the doors