double leaf effect cost more than triple in most situations.

This is a similar design to lou's studio. The center walls are built first and they connect to the outer walls and the floor/ceiling. Then the inner rooms are floated, I assume the walls are built on the floor, the outer skin is added then the walls are stood up and the inner skin is added ending up with 6 leafs. 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!! Eric and a Professor in acoustics from Brussels were the only people prepared to guarantee the 100STC and I gather Eric devised the 2 leaf system to achieve it and ended up designing the acoustic isolation system used. I understand the glass used in the 2 pane windows was 4" thick!! http://www.galaxystudios.com/music/#/st ... laxy_hall/ Hopefully Eric will stop by and confirm this.

cadesignr wrote:

PLEASE...can someone tell me what I'm missing, cause I'm missing something. I mean, I see these sort of things in Mr. Newells book as well. What is going on?

It is actually a straightforward compromise in specification. Muliple leaf has greater isolation than double leaf in high frequencies, and less at low frequencies. If high isolation is not spec'ed at low frequencies, then multiple leaf is better. Well specified, Andre

It is actually a straightforward compromise in specification.

What part of this didn't you understand andre?

Isolation Specification The isolation specification is based upon both the isolation from the building and isolation between rooms. Low frequency cross-talk (isolation) between adjacent studios.

If its so straight forward, then why did they use 6 leaf for LOW FREQUENCY ISO?

Well specified,

I'm not convinced.

John Sayers wrote:

I understand the glass used in the 2 pane windows was 4" thick!! http://www.galaxystudios.com/music/#/st ... laxy_hall/ Hopefully Eric will stop by and confirm this.

In Phillip Newell's book, Recording Studio Design, the Author makes mention of this studio. It wasn't specifically a flattering comment, but it was made in passing, so to speak. I would have to re-read the book to locate the passage, but if it comes up in conversation, I suppose I will find it :) Nevermind what Mr. Newell said, Eric Desart is a premiere force in the world of acoustics as any one how has read his comments over the years can testify, the shining light that led me home...well, to here, which is sort of my home :)

cadesignr wrote:

What part of this didn't you understand andre?

Isolation Specification The isolation specification is based upon both the isolation from the building and isolation between rooms. Low frequency cross-talk (isolation) between adjacent studios.

If its so straight forward, then why did they use 6 leaf for LOW FREQUENCY ISO?

The section you quoted was a section title. The picture beside the section is captioned as being typical construction. Looking at what is in the picture, that specific partition appears to be between the main tracking room and an isolation booth. The impressive isolation figures shown later (51 dB@63 Hz) is not achievable by lightweight construction. Examples of what amount of TL is acheivable with such construction can be found in BBC RD 1995 06. As a starter fig 5 on pdf page 8 shows several several multiple leaf walls. The best isolation at 63 Hz is 32 dB achieved with a double leaf construction. All other partitions have lower isolation due to the reduced spacing, increasing the MAM resonance frequency. The higher frequencies are better isolated with more leafs. Higher LF isolation is typical of double leaf CMU construction. Fig 13 on pdf page 19 in NRC IR 586 shows 42 dB TL at 63 Hz with two 90 mm CMU leafs on isolated mounts. Impressive, but still 10 dB less than what was achieved on your linked page! The constructions used to acheive ~50 dB of TL at 63 Hz for adjacent spaces would be considered heroic, even by our studio isolation standards. Without comment, fig 9 on pdf page 12 in BBC RD 1987 01 shows 2 partitions that acheive such performance. I hope this helps clear things on the use of multiple leafs in studios. Clearly leafy, Andre

Nevermind what Mr. Newell said, Eric Desart is a premiere force in the world of acoustics as any one how has read his comments over the years can testify, the shining light that led me home...well, to here, which is sort of my home

Hello xspace. This is exactly why I posted my questions, as I too have bowed on the alter of his High Acoustical Majesty. I was NOT questioning Mr. Desart in any way, shape or form if that is indeed what you are suggesting above. On the contrary, it is BECAUSE of my trust in Mr. Desart that I posted this. In that regard, let me clarify this further. PRECISELY, the reason for my questions is this. From the time I was introduced to the subject of TL, I have been "led to believe", that a TWO LEAF system is superior to multi leaf systems ..PERIOD. So, when I see ANYTHING, that suggests that my belief system has been in error, then I ask questions. In this particular case, I was under the "impression", that modern practitioners of Studio design and construction would use 2 leaf systems as a matter of current acoustic "common sense", if not by their credentialed access to Lab test data of current Scientific studys in the rhelm of TL. Namely, access to University labs, standards, membership in Societies with access to published reports, costly books, etc etc., of which layman such as myself do NOT have nor need as I am NOT a practitioner of Professional Acoustical services. Therefore I can only read what is and has been posted on various forums, and the net in general via Web sites etc. Which is why this question came about. When I came across the linked site, I saw the pictures and immedietly scratched my head. I wondered exactly what I posted. WHY IN THE WORLD, if TWO LEAF SYSTEMS are the "de facto" standard in TL assemblys, would a Company with Acoustical professional staff, design a studio usind MULTI LEAF SYSTEMS???????? At the moment, it appeared as a "no brainer", given my limited knowlege and "belief system". With that said, lets move on. Now, given andre has posted this....

The section you quoted was a section title. The picture beside the section is captioned as being typical construction. Looking at what is in the picture, that specific partition appears to be between the main tracking room and an isolation booth. The impressive isolation figures shown later (51 dB@63 Hz) is not achievable by lightweight construction.

Ok andre, I read the PDF's you linked. Apparently, IF the assemby in the pictures are indeed "lightweight construction", you are correct. Which means, if I understand your statement correctly, and if I may be frank if not blunt, I submit lets call a horse a horse...whoever wrote or designed that page, with the approval of the Company in question...is a DAMN LIAR!!! :evil:

The constructions used to acheive ~50 dB of TL at 63 Hz for adjacent spaces would be considered heroic, even by our studio isolation standards. Without comment, fig 9 on pdf page [removed] 1987 01 shows 2 partitions that acheive such performance.

Hmmm...without comment? If indeed, my presumption is the case, it only confirms my growing other belief system, which I won't go into here, other than freely applying a quote from Mr. Savant on another forum

And the industry is fully aware of this, albeit not seemingly very forthcoming when it comes to discussions about it.

If I'm missing the point of your statements in this regard, then please andre, what is it?

Cadesignr: Acoustics, in studios is a very frustrating thing to fully comprehend because so little is intuitive, significant factors change with un-obvious causes and test data seems to be hard to get. A lot of your frustration I went through myself when learning acoustics. You have my sympathy and admiration for what you are putting yourself through. There is a lot of test data available on the internet if one knows where it is. One of the beauties John's website and his disciples is that we share that knowledge with people who ask. However it is frustrating for people learning to have their beliefs destroyed by facts. I avoided commenting on the BBC high TL walls to avoid diluting the content of the post. Looking at those partitions, they are obviously multiple leaf. In those cases the mass is so high that the MSMSMSM resonance is so low that the partition exhibits the desired high TL right down to the LF range. These are partitions with so great a mass that they would be rarely needed for normal isolation. But it is the correct design in those cases. Keep on learning and don't worry about the headaches trying to learn the acoustics. The headaches will disappear in several years. Andre

"Hello xspace. This is exactly why I posted my questions, as I too have bowed on the alter of his High Acoustical Majesty. I was NOT questioning Mr. Desart in any way, shape or form if that is indeed what you are suggesting above." Actually I was just making a real world connection between Newell and Desart in direct reference to the thick glass that John had brought up.

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!!

Hello John, I forgot to thank you for your reply. However, read on. If I'm not mistaken, your "2 leaf system" statement above may be in for a bit of review. Frankly, untill someone clears up the term "leaf", I'm ready to chock all these years of reading up to a "a lesson in hindsight" :roll: Now let me address andres last post. Hello andre. Sorry it took a while to get back and thank you for the links. Actually, it took a while to analyse that document and then recover. :mrgreen: . I didn't see it before.

Acoustics, in studios is a very frustrating thing to fully comprehend because so little is intuitive, significant factors change with un-obvious causes and test data seems to be hard to get.

To say the least andre.

However it is frustrating for people learning to have their beliefs destroyed by facts.

On the contrary. i don't mind that so much. But what IS frustrating is to BUILD a belief system on what people present as fact, only to find the "facts" turn out to be something entirely different in the firstplace Let me put it this way. How many THOUSANDS of threads, here, at Studiotits, and other forums(even this thread), have posts from experts(Brian Dayton, Rod Gervais, Eric Desart, yourself and multitude of others) offering test data "proof" that TWO LEAF systems are superior to mutileaf systems. Not to mention pictures showing what a TWO LEAF system is. Now, correct me if I'm wrong, but from everything I've read, a TWO LEAF system is defined as TWO distinct quantities of MASS, seperated by an airgap. Whether or not a stud creates the airgap is irrelevent. I've also been led to believe, this is called a MAM system, and or a DOUBLE LEAF system as well, no? So, if that is indeed TRUE, what does one do under those circumstances other than come to a conclusion these are so called "facts", and speak for themself. Now I find this MASSIVE piece of hidden information, and after ALL THESE YEARS, I am not just frustrated....frankly I don't have words for it. The other thing that makes me frustrated is CONTRADICTION in not only the FIELD of Acoustics, but with some people statements that APPEAR to contridict themself. Here is what I mean,

As a starter fig 5 on pdf page 8 shows several multiple leaf walls. The best isolation at 63 Hz is 32 dB achieved with a double leaf construction.

I must appologize at this point. I did NOT see that link the first time I read your post. However, now that I HAVE read the entire linked document, something is not jiving here. First you say

fig 5, Page 8 shows "several MULTIPLE LEAF WALLS"....

But when I look at both fig's 5 & 6 on that page, the author labels these as DOUBLE LEAF!!!! From everything I've read, including this thread, I've been led to believe these are exactly what you call them...multileaf..not double leaf. Then you say....

The best isolation at 63 Hz is 32 dB achieved with a DOUBLE LEAF construction.

So I looked at the link again and immedietly got FURTHER confused. This is why. APPARENTLY, I do not understand the term LEAF, as the BBC author implys a LEAF can be a MAM assembly, which in this case is a STUD partition wall, sheithed on BOTH faces with a layer of mass. He calls this a SINGLE LEAF, which contridicts everything I've read over 10 years. Right from the beginning, on (PDF)Page 5, the BBC author says this:

Fig. 2 shows the sound insulation of a staggered stud partition compared with those of other single leaf partitions.

Even, the heading below the figure states these are SINGLE LEAF assemblys Apparently, I'm not the ONLY one who is confused. Here is why. The author calls a standard partition wall(TWO MASS's seperated by a stud which creates an airgap), a SINGLE LEAF. From everthing I've been led to believe, this would be called a DOUBLE LEAF, no? Even you call the figure at the top of fig 7, ..a DOUBLE LEAF, which is the one with measured isolation of 32db at 63 Hz. But then the author calls the two assemblys below it DOUBLE LEAF as well!!! Now, even this thread has defined a TWO leaf system, as well as a THREE LEAF and FOUR LEAF system, no? This is why I labeld the pictures on my first post....a SIX LEAF system. But apparently, this is NOT the case, as here, the BBS author calls ALL the examples in fig. 10(page ) TRIPLE LEAF!!! Even the one at the top that is a typical MAM assembly(2 distinct MASS layers seperated by an airgap). Again, in Figure 11, the author calls these different types of assemblys,....TRIPLE LEAF. Which now gets really confusing as I see FOUR distinct MASSES, seperated by THREE AIRGAPS, Yet in other figures(5 & 6 for example) they show the EXACT same thing(4 distinct Mass layers and 3 airgaps, but now the author calls these DOUBLE LEAF!!! And THEN, he calls this a DOUBLE LEAF, which from everything I've been led to believe, is a TRIPLE LEAF!! What the heck is going on here????? I don't understand how an airgap created by a stud is any different than an airgap with NO stud...as in Figure 5c, 6c, 8c. To be absolutely clear, the author states this. On PDF Page (9)

The results are shown in Fig. 8(a) (overleaf). The first leaf was made from conventional 70 mm studs fitted with a layer of 15 mm plasterboard and a layer of 9.5 mm plasterboard each side.

FRUSTRATION?????? What a massive understatement andre. I rest my case. So, WTF is going on here???? On a lighter note, in another section, the author states

the first layer is 19mm "gypsum board but the next layer is 12.5mm plasterboard

???? I thought "plasterboard" was just another name for drywall, which is made from "gypsum". Apparently not. What is Plasterboard made from? Here is the Legend. btw, I'v never seen those metal stud types with another "H" shaped flange. How does one get the drywall into the flange? It would appear they would have to assemble the studs around the drywall first, and then fasten the whole assembly in place. GAK! :shock: :shock:

Keep on learning and don't worry about the headaches trying to learn the acoustics.

Headaches? I get no headaches andre. However, this reminds me of someone on another forum who replied to one of my threads, and implied I take "meds", which implied there is something "wrong" with me. From what I see now, I'd submit I am correct when I told him....it appears the shoe is on the other foot. Afterall, one of his posts was the first time I read an explanation of a TWO LEAF SYSTEM. :roll: I believe the shoe fits him perfectly now. :roll: :roll:

Thanks for the excellent post just above this one. Acoustically speaking, your definition of leaf as a single mass is correct. The strange use of double triple and other in the BBC document relates to use of leaf in construction at the BBC. NOT THE ACOUSTIC TERM. I hope this helps trying to understand teh world of MAM. As you noticed, in the earlier BBC doc I linked it is a 4 leaf system. The mass is so great that the raised MAM... frequency is still so low that is not significant. There is an accurate description of the effects of multiple leafs by Sharp. Unfortunately I do have the link handy. IT is a very technical document, and full of useful information. As far as meds go, aspirin bottles are cheaper by the gross. With fewer headaches, Andre

The strange use of double triple and other in the BBC document relates to use of leaf in construction at the BBC. NOT THE ACOUSTIC TERM.

Good thing doctors don't use different terms than pharmacists. :roll: How preposterous. Well, somebody better let the Studio "construction" forum know. They might be building all kinds of stange walls over there by now. :mrgreen:

"This is why I labeld the pictures on my first post....a SIX LEAF system. But apparently, this is NOT the case, as here, the BBS author calls ALL the examples in fig. 10(page ) TRIPLE LEAF!!! Even the one at the top that is a typical MAM assembly(2 distinct MASS layers seperated by an airgap)." Figure 10 does not show a blanket comment on all the pictures. The items are marked (a), (b) and (c) respectively and the author points this out in the "comparisons" he makes to (a) "...the sound insulation of the single-sided alternative to the triple Camden (Fig. 10(a))" and (b) "...the sound insulations of the simplified triple leaf partition (Fig. 10(b))" The author makes clear, to me, that item (b) and item (c) are the triple leaf he is discussing. A typical residential wall, the author refers to this wall assembly as one leaf due to the coupling. I am guilty of saying two leaf as anyone else may be, which does not jive with the standards used in this document...but I am not a scientist either :) I consider the document accurate, my use of the terms here and in the outside world a simplification even if in-accurate as this document recommends. But for the most part, I think we are still in the same ball park.

my use of the terms here and in the outside world a simplification even if in-accurate as this document recommends.

I'll remember that the next time you speak of a double or triple leaf. Only problem is...which one will you be refering to? :roll:

the one we've grown accustomed to no doubt.

With all due respect John, I don't understand why the cynical tone from xspace and you. : One would think this community at large would welcome news that the use of certain concepts/terms used here MAY have been in error, and even if not, when other SIGNIFICANT, RELEVANT and seemingly IMPORTANT information in this regard is presented to this forum, it's like stepping on peoples toes, especially if it CHALLANGES prevailing schools of thought and studio design dogma..scientific or not. This document proved to me, the use of multileaf assemblies to achieve very high isolation values are in used in a variety of ways by the foremost authority on Studio construction, which when I read it, seemed to use a certain term in ways that were in conflict with everything I've been led to believe. I posted this NOT to step on peoples toes, but to learn. Thanks to andre, I saw concepts that have NEVER been discussed on ANY of all the relevant forums I've been visiting for over 10 years, and after viewing these concepts, something didn't jive.. But when I post a relevant set of questions..other than andre...what do I get? :roll: among other things...scoffing tone, rolling eye attitude, in-significant error checks......

Figure 10 does not show a blanket comment on all the pictures.

Since you want to get picky.."Figure 10" is indeed blanket LABLED....which is WHAT I WAS REFERRING TO! :evil: :roll: Afterall, I posted FIGURE 10!! Here it is AGAIN for verification. What does the LABLE say? :roll:

The author makes clear, to me, that item (b) and item (c) are the triple leaf he is discussing.

Then I assume if "I" were to refer to a TRIPLE LEAF assembly on THIS FORUM...FROM NOW ON, you will understand what I am talking about. I also assume YOU will take your valuable time to explain to others that my use of the terrm is NOT the "norm" used on this forum, no? :roll: Indeed, you will also take the time to explain...WHICH TRIPLE LEAF I am refering to...the one with THREE distinct masses and TWO airgaps, or the one with SIX distinct mass's and FIVE airgaps, eh? I also assume YOU will continue to use..as John puts it..

the one we've grown accustomed to

In that case, now that SIX LEAF(or in BBC terms..TRIPLE LEAF) systems have been discussed, when YOU refer to a SIX LEAF system, I will assume you will also take the time to explain WHICH ONE you are referring to...the one with SIX distinct mass layers and FIVE airgaps which have a TWO LEAF COUPLED assembly surrounded by TWO non-coupled masses on the exterior layers, OR, the one with SIX LEAFS, which have FIVE airgaps, but is made from THREE coupled TWO LEAF assemblys, whereby the OUTER assemblies are NOT coupled to the inner assembly...no? Have fun.

A typical residential wall, the author refers to this wall assembly as one leaf due to the coupling. ,

Then I assume from your analysis item 10a would NOT be what he calls ONE LEAF? Now, because there is no coupling(regardless that the studs may be COUPLED at the floor and ceiling) it is neither a ONE leaf, Double leaf or Triple leaf...it is simply....er.....something he refers to as...SINGLE SIDED...hmmmm. Boy, I bet a homestudio builder would have fun trying to describe THAT scenario to a carpenter. Ha!

I am guilty of saying two leaf as anyone else may be, which does not jive with the standards used in this document...but I am not a scientist either

Scientist? What does it have to do with science? Its simply a matter of DEFINING the term LEAF, which was the WHOLE point of my post. geeezus xspace, what part of this needs a Scientist to explain it to you. I did NOT ask for Eric or anyone else to provide "scientific" analysis or Lab test results. I just wanted a damn CLARIFICATION of the term LEAF! And guilty? See below.

I consider the document accurate, my use of the terms here and in the outside world a simplification even if in-accurate as this document recommends.

Simplification? I would think the author himself is the one who has "simplified" the term leaf, although it appears it has become grossly complex, and therefore confusing. At least when compared to, as andre put it...the ACOUSTICAL way or the "customary" use here. :roll: And in-accurate? ahh...I'm getting confused again.

But for the most part, I think we are still in the same ball park.

In the same ball park???? Good god, Andre JUST SAID...the term "LEAF", as used here is CORRECT!!!! So why are you trying to make it look like even if the use here is INCORRECT...your "still in the same ball park???? What kind of non-sense is that? Andre just explained the BBC uses the term in an entirely different context. sheeeesh! :roll: Thats like..."its ok...were exempt from correct usage because "we" know what "we" are talking about"!!! You'd make a great attorney xspace. :wink: Even John just said..." the one we've grown accustomed to no doubt." Unbelievable. Frankly, this is EXACTLY what I expected here. Although I'm somewhat suprised Stuart hasn't jumped on the pile yet. However, I STILL have questions regarding this whole ball of wax, and at the risk of playground clique abuse, I will ask them regardless if I get a coherent answer. But I think I need a drink first. A STIFF one. :roll:

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... :) - Stuart -

Hmmmmm...

I could tell you why,

Ok. So you see it too.

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.

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/

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?

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

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". - Stuart -

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?

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

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?

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! :)

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! - Stuart -

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....

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.

With all due respect John, I don't understand why the cynical tone from xspace and you. :

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...

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....

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...

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....

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...

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

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.

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

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...

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..

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....

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?????????

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

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.. .

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)

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.