CLD gypsum

[Bob]

Let's say I wanted to try CLD between gypsum involved in a double leaf wall myself.
Assuming a budget of $200, how would I test it?

[Paul Woodlock]

Let's say I wanted to try CLD between gypsum involved in a double leaf wall myself.
Assuming a budget of $200, how would I test it?

whta's CLD?

Paul

[Bob]

The latest interesting fad over at AVSForum is putting goop between the layers of drywall. Not contact cement, but a viscoelastic or other damping material. CLD is constrained layer damping.

I have an opportunity to get some goop for free.
But there's also
http://www.quietsolution.com/constructi ... sives.html
http://www.soundown.com/Product%20Line/ ... erials.htm
and a few others. There's also thicker stuff like ASC WallDamp, but I've been told that thin (less than 1/16") is best for CLD.

[Rod Gervais]

The latest interesting fad over at AVSForum is putting goop between the layers of drywall. Not contact cement, but a viscoelastic or other damping material. CLD is constrained layer damping.

I have an opportunity to get some goop for free.
But there's also
http://www.quietsolution.com/constructi ... sives.html
http://www.soundown.com/Product%20Line/ ... erials.htm
and a few others. There's also thicker stuff like ASC WallDamp, but I've been told that thin (less than 1/16") is best for CLD.

You call it "goop" they call it adhesive. ASC wall damp is just an easier way of creating laminated panels. Not quite as messy as other methods.

It doesn't matter what type of adhesive it is - it's just another way of creating a laminated panel........... it doesn't work from my perspective........ I avoid laminated panels like the plague.......

Rod

[Eric.Desart]

Hi Rod,

You should know Bob by now :):):)
He tries everything. As long as it is not simple or standard and used by anyone.

Now serious.

Bob this really isn't easy to test.
Bob if you want to know what this can bring, compare monolithic glass and laminated glass from the same total thicknesses.
Think that for gypsum walls the difference will be smaller. Reason: the start internal damping of mounted gypsum walls will be lower than for monolithic glass.
The basic idea however is similar. But that's covered before.

If you want to measure:
You only can do it on single leafs (laminated or double leafs).

Really measuring a double wall is hardly possible since you must make sure that the surrounding TL must at least be 8 dB better, in all frequencies, than the TL to be expected from your wall. I should say that's wishful thinking.

If you measure with one leaf, you can try the door opening in a wall were you put in your panel.
However you must be aware that at certain frequencies the surrounding wall will become defining.
So the better your measurement object, the more trouble you will have to get representative TL data, not influenced by surrounding things.

Then you get a gross insulation.
However such result is influenced by the room acoustics at the receiving side.
So in fact you must measure reverb there, from that total equivalent absorption and correct the immission level with that.

But if you don't look for absolute values but a relative comparison it becomes easier. Just build different versions in whatever hole where the TL of the surroundings clearly exceed the TL you expect from your samples.

There are other methods which allow easier measurements based on intensity measurements but:
a) that's complicated
b) calls for experience
c) calls for very expensive equipment and a 2 channel measurement system. Only the microphone probe cost > 25 times your planned budget.

In other words.........
No other words.

Eric
PS: Bob, you're a maniac (but that can be positive too).

[Paul Woodlock]

Greetings

I would like to software model the entire universe from Big Bang to Big Collapse in Stereo.

I have a budget of £4.53. How should I go about this?

Cheers in advance

Paul

[Bob]

I figured this would be beyond me (hardware and training and price).
Instead of measuring sound db, could I measure deflection with something?
A laser. An interferometer. Something.

Someone suggested that it would be $20 to do a DIY test, but it turns out that what they meant wasn't a double leaf wall TL test, but just a single leaf {gypsum, goop, gypsum} resonance test.

______________
The happy maniac :)

[Bob]

BTW, for the double stud wall test, what I was envisioning was building a pair of five sided boxes, sort of like Paul's Fan Silencer Box -
1"MDF/Plywood/1"MDF inner box then 4" rockwool then 1"MDF/Plywood/2"MDF. outer box
The box would be about 3' long, and have a 16"x16" open end (internal measurement)

Put the speaker in one box, then screw and caulk on the test leaf.

Put the microphone in the other box, then screw and caulk the other leaf.

Set them both on sand, with the test ends about 8" apart facing each other.

Put some rockwool in between them


With the box so small, I was hoping that the modes might be higher than the frequencies I'd be interested in.
Fire up the speakers and record with the microphone.

[Eric.Desart]

Hello Happy Maniac

I figured this would be beyond me (hardware and training and price).
Instead of measuring sound db, could I measure deflection with something?
A laser. An interferometer. Something.

Someone suggested that it would be $20 to do a DIY test, but it turns out that what they meant wasn't a double leaf wall TL test, but just a single leaf {gypsum, goop, gypsum} resonance test.
______________
The happy maniac :)

This is NOT or HARDLY possible.
In fact what you're looking for is recalculating vibration into sound radiation.
So in fact using an accelerometer.
But since you don't have one substituting this by an alternative way of measuring amplitude and frequency.

I once explained this before:
When you are measuring heavy walls as concrete or brick walls, you are measuring above the coincidence frequency (which is very low).
There the wall will vibrate as a piston. On such a wall one can easily recalculate the vibration data into sound radiation, since above the coincidence frequency the radiation degree is 1, meaning that any bit of vibration you measure is transformed in sound radiation.

However for flexible walls were one measures below the coincidence frequency the radiation degree will become lower to much lower than 1.
This means that there is in fact some kind of natural anti-noise in front of the panel. The over and under pressure caused by the short bending waves in the panel will cancel one another partly (pressure and under pressure toggles between crests and troughs).
This is a very complicated business.
So even when you should manage to measure this amplitude and frequency, it's very hard to do anything sensible with the results.
You also should notice extreme deviations over the panel surface (edge clamping - modal behavior in the panel etc.).
So forget this approach.

The small box thing is only sensible for high mid to high frequencies (is sometimes used as demonstration for teaching or science institutes).
So it's certainly not sensible for what you're looking for.

The only reasonable thing is this hole in a heavy brick (or whatever) wall as e.g. a door or window opening or something.

Best regards
Eric

Addendum:
You're for me THE typical studio guy.
You assume that the whole world outside the studio world must have missed something important to investigate.
Mostly there a simple rule: If an approach is not used outside the studio world it means it's not worth bothering.
The non-studio building world must be thousands of times bigger than the studio world. Most investigations are done by the highest qualified people and institutes for this much larger market.
All those practices are only sensible and can be sold inside this studio world, were for some strange reason they think to be cleverder or something when it relates to sound.
If something can be cost effective applied it should be standard applied already long time ago. Ther's NOTHING new about the effect and physics of internal damping. And no magic material or application can suddenly change this physics.
But hé studio people like magic.

Anyhow
Warm regards and until the next special idea :):):)

Eric

[Bob]

OK, this is dead. Thank you.

(I do have a little basement window, and I could put the speakers outside and the microphone inside, but I doubt that I'd get the +8db requirement)

[Bob]

(humor)
Anyone know where I can get a testing facility like this one for under $200?

http://irc.nrc-cnrc.gc.ca/fulltext/ir811/ir811.pdf page 15 and 16

[Brian Dayton]

digging around on the old pages, another interesting thread...

If something can be cost effective applied it should be standard applied already long time ago

superchunks are pretty cost effective, and don't seem to be the standard applied long ago...

philosophizing: there is sound logic in that sentiment, but if taken too far or too literally, perhaps it would serve to stop people from trying new things altogether, and that's never in anyones best interest. I/we hear that alot in the paint industry, yet progress presses forward.

Ther's NOTHING new about the effect and physics of internal damping. And no magic material or application can suddenly change this physics

As usual, Eric is correct. no magic to damping at all, and history, theory, and all those nice things teach that damping does two basic things:

1. reduces the magnitude of resonances
2. increases attentuation of waves over distance (wave traveling across something big) or time (wave bouncing back and forth across a slab or bowl or whatever). so if we damped a church bell that long extended ring would become a thuck, so to speak.

your specific question was a double stud wall, perhaps pondering for a moment would let a guy understand how those could apply...

2. i do not believe that 2 would apply to a double-stud wall in a lab-test, because the two layers of the wall are isolated, and the vibration couldn't transfer between them anyway.

however, when you put a code-required firestop into the wall, things change fairly drastically:
http://irc.nrc-cnrc.gc.ca/fulltext/ir-754/
in that case damping may be of aid in reducing sound transmitted through the studrow/firestop junction by reducing the amount of sound effecitvely transmitted to that junction.

1. would affect teh coincidence dip ala the previously posted laminated glass situation. however, in my opinion, this is of fairly trivial value on a double-stud system as TL's at those frequencies are so so high already.
the second area, of more importance perhaps, is the "mass-air-mass" resonance, more aptly termed the "mass-spring-mass" or MSM resonance.

If we had two pistons in a sealed cylinder, damping the pistons would be of no value. adding friction would be the way to provide damping in this case.

i assume that's the aspect you were interested in testing, so... so this post is long enough already.

if you are interested in testing the damping properties of things, that can be done with some labor but minimal cost. let me know and i can post an idea.

[Brian Dayton]

ok, edit:  removing links to equipment that caused someone some frustration

i had pointed out that for 24 bucks and some freeware you could run an approximation of a test here, but i did it in fun, and not thinking that anyone would actually attempt it.

so, i remove, i apologize, sorry for the oddball hole in this thread.

[Eric.Desart]

(humor)
Anyone know where I can get a testing facility like this one for under $200?
http://irc.nrc-cnrc.gc.ca/fulltext/ir811/ir811.pdf page 15 and 16

Bob,

That depends how many you need.
Most likely you can get a quantity discount.

[Brian Dayton]

hey, how's the morning in Europe? i rambled away a good hour on this forum, which i've come to thoroughly enjoy.

[Eric.Desart]

digging around on the old pages, another interesting thread...

If something can be cost effective applied it should be standard applied already long time ago

superchunks are pretty cost effective, and don't seem to be the standard applied long ago...

philosophizing: there is sound logic in that sentiment, but if taken too far or too literally, perhaps it would serve to stop people from trying new things altogether, and that's never in anyones best interest. I/we hear that alot in the paint industry, yet progress presses forward.

Hello Brian,

:-) Are you scared we fall asleep? That you activate those old threads ......
I'm mostly happy when Bob's complicated mind goes at rest for a while (don't reactivate this )

You knew very well what I meant ....
In my "playing with baffles" doc you find the first page of the (now expired) patent of corner absorption.
http://www.acoustics-noise.com/AFBsite1 ... affles.doc.

In fact corner absorption is rather recent. The patent dates from begin the eighties. (Jeff: not 50 years).
It was first used under license by Rockwool Sweden mainly promoted for classroom acoustics and conference rooms.
Rockwool Sweden, previous part of the International "Rockwool international" group to which most European (and few US brands) National Rockwool companies belong, was Nationalized and as such separated from this International group.
Therefore they used an export name outside Sweden: ECOMAX.
However the original Rockwool companies dominating the outside Sweden National markets, weren't interested in this approach, since Ecomax was a competitor for them.

This has blocked this approach very strongly, and little was written about it.

Commercially it's not very interesting. (in the larger picture of acoustics)
In most acoustics (statistical), corners aren't that dominant, and the idea is difficult to protect.

Somehow it got in the studio world, were those very low frequencies are important, room acoustics is not statistically, but as correlated signals treated, and were the corners in function of the small volume are important.

So the comparison I made with cost effective solutions being used outside the studio world does not relate to an application which has relative little application in the thousands times larger non-studio world.

However for insulation and drywalls this isn't true.
High TL values and speech privacy is as much a quality measure outside the studio world as inside. Offices, banks, the HORECA sector plagued by environmental rules, private homes with those annoying children with their Jingle Jangle music (traditional parents interpretation), TV, studying, neighbors ......
Just find the really cost effective solution (even when additional costs are involved) suitable for a mass market, patent it, and you get as rich as in your wildest dreams.

If increased internal damping for practical applications should be cost effective than ANY drywall producers should have this standard in his catalogue at a fraction of the price it's available now.
All those huge companies have experts, or contact with, watching whatever is written or produced.

The Saint-Gobain group developed a new (some 5 to 10 years now) PVB foil (patented) for laminated glass for sound insulation. This foil indeed preserves the coincidence of the original thin panes.
Such developments do not happen anymore in studio groups but as research projects in labs by experts as you are, having HUGE R&D budgets and years of time + own test facilities.
The result some gain in the coincidence area which for standard purposes is not that significant. But mainly for thick panes for a smaller market.
The cost standard laminated glass + 25 to 45% for as long as the patent is valid.
But this group is HUGE (over thousand companies worldwide)

Just some fun thoughts.

[Brian Dayton]

You knew very well what I meant ....

yes, yes, you are right, i realize you didn't mean to say we should stop trying new things.

and i suppose you are right, as technology progresses the capacity of individuals to advance it falls somewhat - for example, long ago 3 guys invented the transistor, but it seems unlikely that anyone is going to advance in Intels chips in their garage.

take care all,

Brian