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PostPosted: Tue Jan 26, 2010 5:17 am 
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among other things...scoffing tone, rolling eye attitude,
I could tell you why, but you probably wouldn't want to hear it...

Besides, I didn't think John's remark was "scoffing" or "mocking" at all! On the contrary, it was humorous, polite., diplomatic even.

The way you take everybody else's comments to be personal mocking attacks on yourself reminds me of a "joke" I heard years ago, when a guy called a "tapiologist" would inspect the wheels on steam trains by tapping them with a hammer, then deciding, based on the sound, if the wheel was cracked or not. He condemned something like a hundred trains before someone pointed out to him that his hammer was cracked...

:)

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PostPosted: Tue Jan 26, 2010 7:12 am 
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Hmmmmm...

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I could tell you why,
Ok. So you see it too.

Quote:
Besides, I didn't think John's remark was "scoffing" or "mocking" at all!
Thats odd, you just said you could tell me the reason why I was correct.

Speaking of cracked. Besides logic, something else comes to mind.

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PostPosted: Tue Jan 26, 2010 7:34 am 
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I don't see how any of my remarks could be interpreted as mocking or scoffing!

In the article you posted they are talking about 50 - 70 isolation figures based on their research in 1995.

Now read galaxy's history where they talk about 100 isolation figures and Eric's research.

http://www.galaxystudios.com/music/#/history/


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PostPosted: Wed Jan 27, 2010 6:27 pm 
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A leaf is not mass. If you consider the leaf the framing then you may get a better picture. When the author says, "double sided" this may well be the confusion. A double sided (READ: two distinct pieces of wall board on one side of one single frame) double leaf (two separate walls) this is what is very commonly called a double leaf wall assembly, ad hoc, two distinct walls with mass on opposite sides.

But it can be used to explain several different items. A concrete block wall with a framed wall in front, rather on the inside, is a two leaf....even though there is no sheetrock on the concrete block.

There are a lot of variables and I appreciate your point of view as to the interpretation of this document. I am not certain if there is a camp that completely agrees that a simple interior residential wall is or is NOT mass spring mass. But there is an undivided community that says mass on one leaf/and air space/ and mass on the other leaf is the way to go, certifiable so.

Your argument...it really is an argument that takes none of those involved to any greater plane...would be welcome were it not for the acerbic fashion that you have projected it to the people that you have learned from, myself not included.

Maybe when you have a few un-disrupted moments you could point out some of the links you have visited that suggest somehow you have been led astray for so many years.

Maybe clarification is in order?

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PostPosted: Thu Jan 28, 2010 12:58 am 
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xSpace wrote:
I am not certain if there is a camp that completely agrees that a simple interior residential wall is or is NOT mass spring mass.

Huh? If by you mean gypsumboard on two sides of a support system as "simple interior residiential wall", there is no question that it is a MSM system. Have a look at IR761. Every wall system has an MSM resonance.

Andre

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PostPosted: Thu Jan 28, 2010 5:37 am 
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I'm with you for sure, André, and I understand perfectly (OK, make that "reasonably well") what you are saying about "leaf" being a terminology issue here, not an acoustical issue, with the BBC paper just not using the word in the way it is used here, today. So my question isn't about that. It is similar, but out on another line, really.

I'm wondering: when does a 2-leaf stop being a 2-leaf?

I get why a standard wall (drywall-studs-drywall) is definitely a two-leaf MSM system, and I get why a concrete block wall with all those numerous small cavities inside the blocks acts more like a one-leaf wall. But I'm kind of curious as to where to draw the line, and what makes the difference. Is it a matter of how stiff the material is? How well it is coupled through the "webs"? Or is it related to density? Maybe the spacing of the webs? Size of the air gaps? Links between air gaps? Something else?

For example, for argument's sake, if you could (theoretically) replace the 5/8" drywall on both sides of a standard wall with high density 5/8" reinforced concrete panels, but using the same studs, screws, insulation, spacing, and anything else, would that still act like a 2-leaf, or would it now act more like a single leaf due to the higher density and stiffness? (Ignore the fact that such a wall would probably be impossible to build: it's just a thought experiment!).

On the other hand, if you could (theoretically) replace the studs in a standard wall with extremely thick, dense, rigid metal plates, and use twice as many of them to get, say, 8" OC mounting, but use the exact same original drywall, screws, insulation, etc., then would that act more like a single leaf, or would it still act like a 2-leaf?

I imagine that this isn't a simple answer, that it is really rather complex, and depends on a number of factors, but I'm trying to get my head around the concept of "when does a 2-leaf system with mass and air gaps stop acting like a 2-leaf system".


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PostPosted: Thu Jan 28, 2010 7:33 am 
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The BBC leaf section refers to the top and bottom plate connections as well.
Is there theroy- if your sharing a plate then it's one leaf?

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PostPosted: Fri Jan 29, 2010 1:30 am 
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Good question Stuart. Unfortunately I can not clearly and succinctly answer the question. Regarding your wall example, it still is 2 leaf. The controlling factor is the coupling between the leafs. Oops, I think I just did answer the question clearly and succinctly. Sorry about that. :D

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PostPosted: Fri Jan 29, 2010 4:31 am 
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Regarding your wall example, it still is 2 leaf. The controlling factor is the coupling between the leafs.
Ahhhh! That's kind of what I suspected. Thanks! Makes perfect sense.

So my SECOND wall example above (with lots of rigid, dense, thick steel "studs" close together on 8" centers) would be heading in the direction of acting more like a single leaf, probably, rather than a 2-leaf? Correct?

Quote:
Oops, I think I just did answer the question clearly and succinctly.
Hehehe! When did you ever answer otherwise!?!? I would have it no other way! :)

Quote:
Sorry about that.
No apologies necessary! You said all that needs to be said to get my thinking on the right track. As always!

Thanks!


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PostPosted: Sat Jan 30, 2010 6:33 am 
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Hi guys. Sorry it took a while to get back. For some reason the bbs isn't emailing me when there is a reply to a thread I'm watching.
Anyway....

Quote:

I don't see how any of my remarks could be interpreted as mocking or scoffing!


Ok, but just for accuracy sake, this is what I really said John.
Quote:
With all due respect John, I don't understand why the cynical tone from xspace and you. :


Quote:
scoffing tone, rolling eye attitude, in-significant error checks......


I don't see the word "mocking", do you?...you put words in my mouth.

My point was, I tried to bring something of relevant interest to the forum. What I get back is like " a defence" of the common use of the term leaf"...but in a scoffing "tone". Like rolling your eyes at something that SHOULD be important to you, but you want to pretend that it isn't. I mean, people are asking questions now, no?


Ok, maybe I over reacted John, but it comes from MANY previous experiences here,. Anticipation of flaming is my only defence.

Well, lets drop it, ok?. I APOLOGIZE if I was incorrect.

However, there are still a few things to clear up though. This WHOLE leaf thing STILL is up in the air as far as I'm concerned. For instance, here's yet ANOTHER conflicting set of statements
Andre states...
Quote:
Thanks for the excellent post just above this one. Acoustically speaking, your definition of leaf as a single mass is correct.


Which is odd, as xspace says this AFTER andre confirmed my interpretation....
Quote:
A leaf is not mass.


This is why I get frustrated. Ether it IS or it ISN'T!!! Again, how many THOUSANDS oif references can be found on this forum alone, that defines a LEAF as a membrane of MASS, no?

But then he goes on...

Quote:
If you consider the leaf the framing then you may get a better picture. When the author says, "double sided" this may well be the confusion. A double sided (READ: two distinct pieces of wall board on one side of one single frame) double leaf (two separate walls) this is what is very commonly called a double leaf wall assembly, ad hoc, two distinct walls with mass on opposite sides.


This is absurd...... DOUBLE LEAF(two seperate walls)
A DOUBLE LEAF WALL ASSEMBLY????? IS VERY COMMONLY CALLED....WHAT???? That statement is completely at odds with not only the content of this thread, but the common use of the term LEAF on this bbs......I've NEVER seen anything you or anyone else has ever said that aligns with this statement. In fact, if thats the case, then even this statement becomes somewhat of a misnomer....
Quote:
the one we've grown accustomed to no doubt.


So John, exactly what is this definition "we've grown accustomed to...NO DOUBT!??? hmmmm? It sure isn't tthe the way the BBC uses it, and never has...at least from what I've read here, and ALL OVER THE NET!!

This is what I mean by contridiction. SHOW ME, ANYWHERE on this bbs, where the term DOUBLE LEAF is used or defined as xspace says ..a DOUBLE WALL is VERY COMMONLY CALLED a DOUBLE LEAF WALL ASSEMBLY, and I'll eat my goddamned hat!!! GEEEEEZUS, even Andre said I WAS CORRECT!!!

Unless Erics "double leaf" is something ENTIRELY DIFFERENT than the way its used on this bbs, even YOU used the term as andre said is CORRECT...
Quote:
The 2 leaf system was proposed by Eric Desart when he built Galaxy studios in Brussels. The design was an Eastlake Audio ( http://www.eastlake-audio.co.uk/ea_news.html ) project but the client wanted one main recording room with 3 control rooms fronting onto it and they wanted 100db STC between all 4 rooms!!



Ok, enough of that for now. However, there are STILL some questions that come to mind. Let me start with the "100db STC" as you mentioned above. Not only is the terminology of LEAF somewhat of a conundrum, so is STC. At least to ME. This is why.

Read this,
http://www.greengluecompany.com/understandingSTC.php

and THEN tell me how Erics use of 100db "STC" RATED assemblys is in fact a !00db assembly if this article is indeed true.
Here is a quote from the author at GREEN GLUE
Quote:
Why are the folks at The Green Glue Company the only people that talk about this?
We aren’t! In fact, the very recognized ASTM standard which explains how to calculate STC - ASTM E413 - directly warns us that STC is not suitable for most situations.
“These single-number ratings correlate in a general way with subjective impressions of sound transmission for speech, radio, television, and similar sources of noise in offices and buildings. This classification method is not appropriate for sound sources with spectra significantly different from those sources listed above. Such sources include machinery, industrial processes, bowling allies, power transformers, musical instruments, many music systems and transportation noises such as motor vehicles, aircraft and trains. For these sources, accurate assessment of sound transmission requires a detailed analysis in frequency bands.”

The standard itself openly recognizes exactly the limitations that we discussed above. Why these limitations have been so consistently overlooked by novice and expert alike is something we don’t understand.


Astounding. But what I really don't understand is this, from the GALAXY website.

Quote:
The biggest problem was to insulate the lowest frequencies.


Isn't that what every studio designer tries to achieve? Afterall, a rock drummer produces 100dba SPL LOW FREQUENCY impacts, and MOST of the studios people on this bbs deal with ROCK drummers as a given, no?
Peter Newell even says
Quote:
For example, one cannot turn down the volume of a drum kit. Playing
quietly is no solution, because it produces an entirely different tone quality to
playing loud. Realistic drum levels are more in the order of 110 dBA, so
75 dB of isolation (the 110 dBA SPL [Sound Pressure Level] of the drums
minus the 35 dBA acceptable to the neighbours) would be a basic requirement,
though this could be reduced at low frequencies, as will be discussed in Chapter 2


And...
Quote:
The inside to outside isolation is usually dominant, as few studios are sited next to neighbours producing upwards of 110 dBA. As the 30-dBA region is reasonably close to the limit for
tolerance of background noise by either the neighbours or the studio, it is principally
the 110dBA or so produced in the studio that dictates the isolation needs.



Yet, it is commonly stated on this bbs that 2 layers of 5/8" drywall ...in a DOUBLE LEAF assembly, will provide the kind of isolation needed for drums.
Then the author at Galaxy states this..

Quote:
To insulate frequencies as low as 20 or 30hz, Vermier and Desart calculated that the insulation capacity had to start four octaves below. This means it was necessary to find a way to insulating a 30HZ frequency or even lower."

Hmmm, all this makes me wonder after reading this....

Quote:
So why is the STC system used at all?

As frequency falls, the ability of the different labs to get consistent results also falters. +/- 3 STC points from lab to lab is typical, but if the STC system were extended down to, say, 40 Hz, this might increase to +/- 10 STC points or more, making the results basically meaningless.


Meaningless? even at only 40 Hz? errrr........now I'm really getting curious. Especially after reading this from Green Glues article. Hmmm, didn't I read that most labs can't test below 85hz? Then how does one "guarantee 100db iso at 20Hz if you can't even test it in a lab?????????
Quote:
Problem 1 - STC does not correlate at all to low frequency performance.
The graph(see website) to the right shows two walls, one of STC 47, one of STC 48. Note that in the low frequency range – important for music, theaters, traffic, aircraft, and most other real-world noise sources – the lower STC wall is literally 30 decibels better, yet lower STC


And then this
Quote:
Problem 2 - Misleading results due to frequency cutoff.
The 125 Hz cutoff also leads to some very misleading results. Take the two hypothetical walls below. They are both poor walls, with very bad low frequency performance, but one is STC 32, the other is STC 42

Two very bad walls, one gets a bad STC score, the other gets a reasonably respectable STC score. Why??? Because with one wall, the big problem occurs at 125 Hz, inside the STC frequency range, but in the other wall the big problem occurs just below the STC frequency range.

This creates misleading situations where some construction change or product simply causes a huge problem to shift ever so slightly down in frequency and yields a huge gain in STC. Impressive marketing value, but in reality it doesn’t make the wall better at all. So, yes, problems really do occur.


and finally..
.
Quote:
Summary:
The STC score has only very limited relevance for most sound isolation applications because it is calculated in an archaic fashion, it assumes noise sources that are unrealistic for most situations, and it is calculated over a very limited frequency range, ignoring perhaps the most important of the frequency band.
Therefore you should strive to avoid buying products because of high STC, and strive to find products and designs that yield actual real-world reductions in noise level.


sigh................(goes on reading Mr Newell)
Quote:
It can be seen from Figure 2.1 that
60 dB SPL at 3 kHz will be very audible, in fact it will be over 60 dB above
the threshold of hearing at that frequency, yet a tone of 30 Hz would be
inaudible at 60 dB SPL; it would lie on the graph below the 0 phon curve of
‘just audible’.
Consequently, if a flat reading of 60 dB was taken on an SPL meter measuring
a broad-band noise signal in a room, then 25 dB of isolation would be
needed at 3 kHz if the neighbours were not to be subjected to more than
35 dBA. However, at 30 Hz, nothing would need to be done, because the
sound at that frequency would not even be audible in the room, let alone outside
of it.
Hence, providing 25 dB of isolation at 30 Hz to reduce the outside
level to less than 35 dB SPL unweighted (i.e. a flat frequency response) would
simply be a waste of time, money, effort and space.

I guess I'm just a dummy. I don't get it. Why in the world would the people at Galaxy waste all that time and money to isolate 30hz, not to mention 20hz at 100db...if as Mr. Newel states..."yet a tone of 30 Hz would be
inaudible at 60 dB SPL,"..........".NOTHING WOULD NEED TO BE DONE"! )$^&^*^(_)_((_&^&$##^&&**))))_)_))()&(

What am I missing?

I think its time for a drink.....make that a double.


Just to be on the safe side John, IF you were mistaken by quoting STC as a rating used by Galaxy, something else comes to mind then. But I've had enough brainburn today.

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PostPosted: Sat Jan 30, 2010 12:15 pm 
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Anticipation of flaming is my only defence.
No, it's your only problem...

Quote:
This WHOLE leaf thing STILL is up in the air as far as I'm concerned.
Well, you might try reading Andrés response again, since he siad it quite clearly, I think: The BBC used "leaf" in that paper in a DIFFERENT MANNER than other places do. For them, any bits of wall that are directly coupled is a "leaf". That's not the same USAGE or leaf as what Eric, John, Rod, André, Ro and all the others are using today, where a leaf is a bunch of mass on one side of an air gap, regardless of whether or not it is coupled to more mass on teh other side of the air gap.

It's just different terminology, for different folks, o the other side of the pond. No big deal, once you understand it.

Quote:
A leaf is not mass.

This is why I get frustrated. Ether it IS or it ISN'T!!! Again, how many THOUSANDS oif references can be found on this forum alone, that defines a LEAF as a membrane of MASS, no?
That's right: It isn't "mass" alone. Perhaps more correctly you could call it mass as part of resonant system. Except for the BBC, who uses the term differently...

Quote:
This is absurd...... DOUBLE LEAF(two seperate walls)
Yeah, that's how the BBC used it. It IS a valid use of the word, so I don0t see what the problem is.

Quote:
what is this definition "we've grown accustomed to...NO DOUBT!??? hmmmm? It sure isn't tthe the way the BBC uses it,
Yep, that's right. The way we use the term here is NOT the way the BBC used it in that paper. You seem to be getting the idea, now.

Quote:
Not only is the terminology of LEAF somewhat of a conundrum, so is STC.
And you are telling us something new? Nobody here (as far as I know) claims that STC is a good way of rating a wall for a studio. It happens to be a STANDARD way of rating walls for other purposes, and it happens to be used throughout the industry, so it is useful from that point of view, as a comparison, but I doubt you'll find anyone here using it as a good way to measure the rating of an average studio wall. Transmission loss is a much better rating, and better still is to draw a graph of the actual TL curve.

HOWEVER: Having said that, a 2-leaf MSM wall that has an STC rating of 100 is one hell of a wall, not matter which way you look at it! If it is that good in the frequency band where STC makes sense, then it sure as hell is going to be pretty darn good in the rest of the band too. It's pretty hard to imagine any way in which it could NOT be good, all the way down to 40 Hz, or 30 Hz, or even 20 Hz. If you understand how STC is calculated, and how MSM systems work, then you'd see that a wall rated at STC 100 is going to damn good, even at 30 Hz.

How on earth would you even go about designing an STC-100 wall, through which you can still hear a drum kit? Maybe if you did a five-leaf MSMSMSMSM with small air gaps and thin drywall, and tuned it to 50 Hz on purpose or something like that... That's the only way I can think if to get a steep enough slope at the low end. But I reckon even that wouldn't do it: I doubt you could get it up to 100.

Quote:
Afterall, a rock drummer produces 100dba SPL LOW FREQUENCY impacts, and MOST of the studios people on this bbs deal with ROCK drummers as a given, no?
Actually, the total is more like 115 dB, and not all of that energy is in the low end. Even the kick has plenty of energy in the mids, and also highs. Even more so for toms, and more so yet again for the snare. And of course with cymbals, most of the energy is NOT in the lows.

Quote:
Yet, it is commonly stated on this bbs that 2 layers of 5/8" drywall ...in a DOUBLE LEAF assembly, will provide the kind of isolation needed for drums.
Really? Where? :) That's kind of a blanket statement if I ever head one! That would depend on numerous things, not just the wall construction.

Quote:
Meaningless? even at only 40 Hz? errrr........now I'm really getting curious. Especially after reading this from Green Glues article. Hmmm, didn't I read that most labs can't test below 85hz? Then how does one "guarantee 100db iso at 20Hz if you can't even test it in a lab?????????
Well, there is this things called "mathematics", and Eric is pretty good at it. He can PREDICT how a wall will act. I have no idea if he did it this way, but one way he could guarantee that is to predict the performance of the wall across the entire spectrum, then measure the part that can be measured, then extrapolate to the rest. If the measured curve matches the predicted curve closely for the part that can be measured, then chance are the rest of the curve will match too. But at 100 dB, who cares? If he's off by 10 or 20, who gives a damn? You still would not be able to hear even a whisper of the gorilla beating the hell out of a major drum kit at that level.

Quote:
However, at 30 Hz, nothing would need to be done, because the
sound at that frequency would not even be audible in the room, let alone outside
of it.
In what way is the case Newel describes there even vaguely related to what John is talking about? I don't see any parallels at all. He's talking about a 60 dB tone on a 0 phon curve, for crying out loud! How on earth is that applicable to Galaxy????? How is that even remotely related to 115 dB drum kit????

Quote:
NOTHING WOULD NEED TO BE DONE"!
Yes, that's right! in teh SPECIFC CASE NEWELL IS TAKING ABOUT, then nothing WOULD need to be done. but he most certainly was NOT talking about anything even distantly related to what Eric did at Galaxy!

Sheesh!

You can't just pull random bits of text out of context from some book or other, and expect it to apply in other totally different contexts.

I was going to spend the time to try to explain more slowly and carefully about MSM tuning, and the different zones of the spectrum and what governs them, and all that good stuff. But then I figure: why would I do that? It's all here anyway, spread all over the forum, available for anyone with the necessary time, will, inclination and intelligence to read and understand for themselves.

Quote:
I guess I'm just a dummy. I don't get it.
:)


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PostPosted: Sun Jan 31, 2010 3:09 am 
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Stu buddy. I tried to be cordial and civil. I even apologized for taking you and others wrong. That was a mistake on my part. You just proved I was dead on, at least in regards to you.

If I knew the answers in the first place I wouldn't be here. But now that I've been here for a while, I AM learning. But not always about studios. I'm discovering there are certain people here who posess knowlege they are willing to share without verbally assaulting peoples intellegence, lack of insight or understanding, skillsets, or any other personal attributes. Like John, Eric, Rod, andre, Ethan, and a few others.

On the other hand, there are those who are scoffing, mocking, self righteous, condencending, pompass assholes, like yourself. Ya know Stu, it was sad to hear of your unfortunate accident at birth. I mean, its bad enough to have ones best parts run down their mothers leg in the first place, but having ones umbilical cord pinched by ones own mother in the second, is astounding. Although, in hindsight, I can sympathise with a mothers intuition. But my god, whats the mathamatical odds against someone visiting Bubbas discount rent-a-brain, only to get one laced with dementia. In your case, I'd submit God has a sense of humor.

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PostPosted: Mon Feb 01, 2010 4:22 am 
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:mrgreen: :mrgreen: :mrgreen: :mrgreen: :mrgreen:
Hah Hah


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PostPosted: Mon Feb 01, 2010 7:02 am 
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strange kind of humor...

I'm neither a native speaker of your language nor have I read this thread in completeness but
something (my guts?) tells me that fITZ's post ain't funny.

sorry guys'n girlz...what was the question?

?

:poke:


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PostPosted: Thu Oct 21, 2010 8:30 pm 
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Hello, first post here, pardon the newbie tone.
First, without turning up the heat on a subject that folks have already broiled a bit much, I have to shared some initial dismay at what Cadesignr may have felt was an epiphany. I too have been wrestling with the implications of what constitutes a Two-Leaf vs. Three Leaf assembly. I can't comment on the BBC's interpretations of the meaning of leaf, other than it may have been likened to the difference in meaning of the term Windows for a carpenter vs. Windows for a computer user (yes there are still some carpenters out there for whom the venerable definition is what first pops to mind).

Anyway, as with many things in the physical world, certain practical considerations might need to be examined (on a case by case basis, of course) as to why a Multi-Leafed design might be preferred over a Two-Leaf assembly. As Andre stated, and I believe is implied by the NCS literature (possibly even the Wyle report), if TL is desired to be higher than possible with a given assembly for higher frequencies (greater than Fr), Multi-Leaf assemblies may be required.

Also, as Mr. Gervais I think stated already, real-world (usually economic) concerns sometimes prevent us from being able to get away from Triple-Leaf designs by removing an existing Leaf in an already finished structure - we have to take the potential loss of LF isolation and compensate in other ways, including added mass.

Regarding this, for certain designs to be physically possible and structurally sound given commonly available materials, especially with structural retrofits, there might not be too many sensible ways to achieve very high TL's without using a multi-leaf system. If one were unable to pour concrete into a stable wall, or use masonry products that made solid, flush (mechanically unified) leafs, this might be a case where it could become necessary.

Also, as I struggle to understand the underlying concepts of the M-S-M concepts, is it not true that any single material might exhibit properties that are both Mass-like and Spring-like, or is this strictly a case of trying to differentiate situations where a solid and a gas are compared? Specifically, are laminates of differing materials considered to be the Mass portion, regardless of differences in their densities? If the Inverse Square Law holds true for acoustics, shouldn't it be possible to design multi-leaf "laminates" whereby the differing leaf densities and distances between leaves would increase in such a way that the overall resonances would not coincide, thereby reducing the effect of unimodal low frequency transmission?

Sorry for the laboring post, inquiring minds want to know.


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