Jeff,
Thanks for your thoughts.
I maybe expand on this later, or do it on a web page.
I do agree what I drafted is a stylized approach (which is what I wrote), more to bring the "numbers game" article in its context.
What I don't understand is, and which is why I don't feel tempted to discuss a mathematical approach and model, that I feel that I have to fight my lungs out, just to help people protecting themselves against misleading info.
The author of the "numbers game" article just publishes things, has no background or data to substantiate any of it, didn't even bother to check any literature, but still (mis)uses it to question measurement data of competing products (even based on a nonsense mathematical approach) and to enhance their own products and pseudo-objectivity (!?!).
This has nothing to do with summarizing things in order to make a concept more accessible for a broader public.
Just by being handy, people just swallow it, don't see the disrespect this represents for themselves, even fight the guys fighting for them.
Maybe I'm just too naive ......
Hence I either stop this (self-protection) or have to find more efficient manners by writing more official, less stylized stuff, where I really will irreversibly expose such authors.
This instead of repeating the same things over and over, without hardly any effect.
Jeff I do respect you a lot, you know that.
Eric
PS: this is frustration speaking
why did you post then messages again and again? i can't understand you, maybe it's a language problem... however, you're posts are also waisting my time, because each time i'm looking for a good advice, but i rarely found one :-(
Maybe glasses can help?
But I can give you good advice here: if you find my posts a waist of your time, simply don't read them, rather than spending time to write that you waist your time reading them.
Eric,
No worries, bro. I have a pet interest in this topic.
Of course, I could provide another - perhaps a fresher? - perspective on THE NUMBERS GAME:
From http://www.ethanwiner.com/acoustics.html and http://www.realtraps.com/art_measure.htm
THE NUMBERS GAME
To understand why MiniTraps outperform other acoustic absorbers it helps to know how such devices are measured at a testing lab. As you read in the previous section, acoustic products are commonly specified by their absorption coefficient and this number ranges from zero (no absorption) to 1.0 which means 100 percent of the sound is absorbed.
Theoretically, this is true. But in the contexts of acoustical treatments and the "commonly" used ASTM C423 test, the absorption coefficient can never be 0.00 and can exceed 1.00...which does not mean 100% of the sound is absorbed.
For example, an absorption coefficient of 0.5 means that half the sound is absorbed and the other half either passes through the material or is reflected.
For normal incidence absorption coefficients, this would certainly be the case. But, again, in the contexts of acoustical treatments - almost always tested for random incidence absorption - it is not the case.
Since no material absorbs all frequencies by the same amount, absorption coefficients are usually given for different frequency ranges.
Although 1.0 is the largest legitimate value possible, you may have seen higher numbers claimed for some products. Needless to say, this causes confusion, and makes it difficult to compare published data.
While there is potential for confusion, numbers greater than 1.00 do not make comparisons difficult. All other factors being equal, an absorber with a 1.10 absorption coefficient at 500 Hz is better than an absorber with a 1.00 absorption coefficient at 500 Hz. This is not difficult. And the values larger than 1.00 are completely legitimate.
Once you understanding how absorption is measured, and how the data can be manipulated - both fairly and unfairly - you'll be able to assess room treatment products and materials more wisely.
Data manipulation is not part of the laboratory method. Of course, in the context of THE NUMBERS GAME, "manipulated fairly" would be an oxymoron. 8)
Acoustic absorbers are tested using methods defined by the ASTM, an international organization that establishes standards and practices used by acousticians and testing labs.
The ASTM is a US-based organization. Absorbers in other countries will be tested in accordance with the standards those countries have adopted. Just so there's no confusion, the ASTM sets testing standards for many industries besides acoustics.
By requiring its members to follow the same rules, materials tested to ASTM standards in different facilities can be compared with confidence. However, a flaw in the test method does not take into account the edges of the material.
Edges are discussed in ASTM C423, Section 9. To summarize, test specimens are to be mounted "in a way that simulates actual installation." A subsequent Section states that edges of materials intended for ceiling installation (i.e., a T-bar grid) should be sealed. A good lab usually asks a client whether the edges of the test specimen should be sealed. Since the edges of wall panels are typically exposed, this is not often done for foam and fibrous panels. Since, to the best of my knowledge, the edges are rarely - if ever - sealed for wall panel tests, it is usually safe to compare the results of absorption tests, provided all other factors are equal to one's satisfaction. If there are any doubts, the manufacturer should be contacted. Section 12 of the C423 test method requires a full test report, which must include a detailed description of the exact conditions of the test specimen in the lab.
Although the edges are exposed when the material is tested, the calculation for absorption coefficient considers only the size of the front surface, and ignores the edges completely. For a panel that is two by four feet and four inches thick, the edges add 50 percent to the absorbing surface during testing, yet they are ignored in the coefficient calculation. This is further complicated because there is no standard sample size. Since a small sample has proportionally more edge than a large one, a sample that's 8 by 8 feet will measure better than one that's 10 by 12 feet, even if they're the same thickness and made of the exact same material.
In practice, multiple panels are placed adjacent to each other during testing, to minimize the contribution of the edges. So when 2 by 4 foot panels are tested, typically eight of them are arranged into a larger square.
A minimum sample size is provided in Section 9. Again, a full test report will show and/or describe the size and layout of the test specimen. (Most labs recommend at 72 ft² sample size; smaller than 64 ft² is typically not recommended).
The test does "ignore" the area of the exposed edges. But, as mentioned above, most every absorber on the market reports absorption coefficients that omit the edge area. Thus, it is largely moot with respect to fair comparisons.
Since the subject at hand is edge effects and how they're related to absorption coefficients greater than 1.00, it might be worth discussing a product mentioned above: the MiniTrap. If memory serves, 8 MiniTraps were tested in the "A" configuration (specimen directly on test floor; no airspace). This yields 64 ft² of face area. Add the edges (of the perimeter - assumes panels are abutted in a square pattern) and you get about 74 ft² of area. The absorption for the array of MiniTraps at, say, 500 Hz is roughly 112 sabins (data all extrapolated from here). So, if the standard method is used, the absorption coefficient at 500 Hz would be
112/64 = 1.75
If the additional area is included - which is not in accordance with the standard method, btw - the absorption coefficient at 500 Hz would be
112/74 = 1.51
which is still greater than 1.00. Thus, it is once again shown that the added area of exposed edges cannot fully account for absorption coefficients greater than 1.00.
Even if all four edges of the panels were exposed (panels spread out), the absorption coefficient comes out to about 1.17. Which is still greater than 1.00.
But even when placed to form a single surface area of 8 by 8 feet, four-inch thick edges still inflate the measurements by more than 16 percent.
This final sentence seems to be insinuating that there is some unfairness going on. If virtually every absorption coefficient is calculated using the method in question, then all the numbers are equally inflated. So, again, the subject is largely moot. The method in question is not perfect, but it is the standard method. If it is not followed, then the data are meaningless outside of their own context.
sidebar on RealTraps page; in main body text of ethanwiner.com page wrote:
This panel (figure could not be linked - see above URLs for graphics) is 2 by 4 feet and 4 inches thick. During testing the four edges add 50 percent to the total surface area, yet they're excluded from the absorption calculations. And when many panels are mounted adjacent on a wall, the edges are not absorbing even though they contributed to the published specs.
During the test, all four edges would not be exposed. The edges of the perimeter of the test specimen would be, and would be omitted from calculations. If the edge area were to be included, the results would no longer be in accordance with the standard method.
When many panels are mounted adjacent to each other on a wall, the configuration is closer to the test method and thus the published numbers (not "specs," btw) will be more applicable. The edges did not contribute to the published "specs." They were omitted from the calculation. Since most - virtually all - wall panels are tested this way, the point is largely moot.
Further, most acoustic panels are meant to be installed adjacent on the wall in a cluster.
This is a generalization. The needs of the space dictate the method of installation. How an acoustical panel is "meant to be installed" is largely up to the designer and installer (and owner...and spouse...). The manufacturer may have its own suggestions, but the needs of the space will dictate how most acoustical panels get installed.
In this case the edges are not available to absorb even though they were when the material was tested.
Most likely, they were not "available" during testing. As mentioned in THE NUMBERS GAME ( :!: ), panels are typically placed edge-to-edge for the ASTM test in order to minimize edge effects.
When an entire wall is covered with four-inch thick panels none of the edges are exposed, so the real absorption is only 2/3 what the published numbers indicate - and those numbers were already inflated!
The area of the "entire wall" is not given, so the statement about the absorption being "2/3 what the published numbers indicate" cannot be verified. If the area of the entire wall is roughly equivalent to the entire exposed area of the test specimen, the absorption could be very close to 1x the published numbers...
Of course, these last few snippets seem to be hinting at the impact the test method has on the reliable use of absorption coefficients in predictive architectural acoustics calculations. Most acoustical professionals are well aware of the limitations of using lab test data in their models and will typically take those limitations into account when selecting acoustical treatments for a room design.
For readers of THE NUMBERS GAME, it is unlikely that there will be much of a need to calculate, e.g., reverberation time. This leads back to the point that the absorption coefficients are fine for comparisons, all factors being equal to one's satisfaction.
The same thing occurs with corner absorbers, as shown in the figure below. (Again, figure can be found in above links.) Unless the vendor describes how these triangle shaped samples were grouped during testing, there is no way to determine how much of the stated absorption is due to the edge effect and how much is due to its effectiveness as an absorber.
For the devices in question, total absorption, or absorption per unit, could provide the necessary information for comparison, but would require modification to the standard test methods to accommodate. Otherwise, comparisons of devices such as these using data obtained from the reverb room method are difficult. I have mentioned (opined) in other threads that manufacturers should follow the lead of RPG and perform low frequency specific measurements on their low frequency devices.
Foam blocks like this are meant to be mounted in a corner, stacked one above the other from floor to ceiling. When measured for absorption four of the five surfaces are exposed, but when installed as intended only the front surface absorbs. So in practice, a two-foot corner wedge like this provides only 65 percent of the absorption claimed. The shorter the wedge, the larger the disparity between the published and actual absorption.
While the intent of this paragraph is understandable, the "65 percent" comment has no basis. The devices would have to be retested with the edges in question sealed in order to determine what the actual difference in absorption would be.
For some products, like a tube trap, it is not practical to specify an absorption coefficient because there is no front surface. In that case the correct way to specify absorption is in Sabins, named for acoustics pioneer W.C. Sabine (1868-1919). The Sabin is an absolute measure of absorption, independent of surface area, and it can be used to compare any two absorbing devices directly and on equal terms.
First, the unit is the sabin (small "s"). As is standard with units derived from a person's name, the unit - spelled out - is not capitalized, but the abbreviation - in this case, "Sab" - is capitalized. (Sorry - pet peeve... :? )
Second, the last sentence here would seem to contradict claims made elsewhere in THE NUMBERS GAME. If such comparisons can be made (and they can be made), then this statement with some supporting instruction to the reader as to how to find information on the absolute absorption of a panel or product would suffice. One short paragraph on this worthwhile concept could replace a lot of the misleading content that preceded.
************
The above is for clarification purposes only - constructive criticism. The author of THE NUMBERS GAME is asked to kindly consider it as such.
All the best! 8)
Jeff,
> [long winded point by point dissertation]
> The above is for clarification purposes only - constructive criticism.
I read all of that - twice - and I still have no idea what your point is. The purpose of my article is to explain how absorption coefficients can be larger than 1.0. It also explains how what's measured in a lab can be very different from what someone will actually get in use, and explains why. As far as I can tell my article does that very successfully. 8)
Thanks for the clarification on Sabin versus sabin though.
--Ethan
Jeff,
> I found a reference to a paper by a W. Kuhl <
Excellent.
> For a sample of rockwool (thickness not given), the midband absorption increased roughly 20-30% for each doubling of exposed edge area. <
Apparently the surface area wasn't given either? That 20-30% figure is totally meaningless without knowing the surface area!
> Increases in midband absorption are directly related to edge exposure and - over a limited bandwidth - could be a simple function of the ratio of exposed perimeter to area of materal, as suggested by Kuhl and Gilford. <
And please don't forget: As suggested by Ethan Winer.
> To expand on Eric's diagrams (and perhaps dispute some of the conclusions in a minor way?) <
I'll let you dispute Eric. Whenever I do that it just makes him even more irate. :)
I will say that Eric should go back and do some more testing. That's the only way he can truly establish how much of the increased absorption is due to each of the four possibilities John Kopec mentioned. It could be that edge surface as I propose accounts for 99 percent of the increase, or maybe it's only 1 percent. Likewise for diffraction and the other possibilities. For any of us to argue the other guy is wrong, but with no hard proof, is intellectually dishonest.
I agree it makes sense that different factors might affect different frequency ranges. This too could be much better understood with a few new more carefully devised tests.
--Ethan
> Increases in midband absorption are directly related to edge exposure and - over a limited bandwidth - could be a simple function of the ratio of exposed perimeter to area of materal, as suggested by Kuhl and Gilford. <
And please don't forget: As suggested by Ethan Winer.
As NEVER in his live suggested by Ethan Winer, but as written by me numerous times as opposed to Ethan Winer, and as much times ignored by Ethan Winer (even in these very current threads).
A perimeter is NOT the edge surface.
To clarify:
The perimeter is written as a measure to the power 1, an edge surface is a measure written to the power 2 or L*W.
See the mini tiny difference ????
One is called length, and the other area or surface ...... (but I agree, why discuss a difference of 1, it's close enough ..... annoying words, numbers, a dimension more or less, who cares?)
It's only a completely different concept, but all this bean counting ...... It sounds about the same ......
Metaphorical:
And if there is a difference (is there?), then these "Kuhl and Gilford" guys must be wrong. As are all the other authors making the same dumb mistake.
They make no sense....... They really should all start measuring again .... with and without foil frame around the absorbers, or they are useless, University Acoustic Departments and Labs, Profs or not.
They all better check with me first .....
My investigations clearly show ..... Hoooow, I forgot: I never investigated anything, even didn't read about it, I only wrote about it. Never mind, it served and still serves it purpose.
End Metaphorical
PS: This factor P/S as model parameter (or S/P depends on model) with P = 'free edge length' and S = 'area of sample':
I've no idea for sure who was first and when, but Morse and Bolt used it already in 1944.
A perimeter is NOT the edge surface.
To clarify:
The perimeter is written as a measure to the power 1, an edge surface is a measure written to the power 2 or L*W.
See the mini tiny difference ????
without taking sides. if the perimeter (of some object) has a incident interface of say 3.5 inches around a perimeter of 8 feet, effectively a 2.3 sq foot presence, does this represent a material aspect to room say of 1775 cubic feet (a small room)? does this become material in if I have say 8 of these (representing 20 sq feet)? not withstanding other measurements, would someone be inclined to differentiate the acoustic response? just curious...
I read all of that - twice - and I still have no idea what your point is. The purpose of my article is to explain how absorption coefficients can be larger than 1.0. It also explains how what's measured in a lab can be very different from what someone will actually get in use, and explains why. As far as I can tell my article does that very successfully. 8)
I will remember this the next time you ask people to "simply point things out" to you if they are wrong, misleading, inaccurate, inconsistent, or otherwise. I meant nothing personal by the above "dissertation." That should have been obvious from my tone. I completely ignored all the off-topic comments and insults you threw at me a few days ago; decided to try and help. The accuracy and scientific substance of THE NUMBERS GAME has come up many times. I thought perhaps with my "dissertation," you would be able to make some changes; make things better. Oh well... :roll:
Thanks for the clarification on Sabin versus sabin though.
Being that you are not involved in math or science in any capacity, it's an understandable error. No sweat. I guess I can be glad the most minor of points got through to you.
> For a sample of rockwool (thickness not given), the midband absorption increased roughly 20-30% for each doubling of exposed edge area. <
Apparently the surface area wasn't given either? That 20-30% figure is totally meaningless without knowing the surface area!
Um, 10 m². Says so right in my post. :)
> Increases in midband absorption are directly related to edge exposure and - over a limited bandwidth - could be a simple function of the ratio of exposed perimeter to area of materal, as suggested by Kuhl and Gilford. <
And please don't forget: As suggested by Ethan Winer.
I could not find any references bearing your name, but I'll take your word for it. Kuhl's paper was from 1960. When did you write yours? What publication was it in?
> To expand on Eric's diagrams (and perhaps dispute some of the conclusions in a minor way?) <
I'll let you dispute Eric. Whenever I do that it just makes him even more irate. :)
I will say that Eric should go back and do some more testing. That's the only way he can truly establish how much of the increased absorption is due to each of the four possibilities John Kopec mentioned. It could be that edge surface as I propose accounts for 99 percent of the increase, or maybe it's only 1 percent. Likewise for diffraction and the other possibilities. For any of us to argue the other guy is wrong, but with no hard proof, is intellectually dishonest.
I agree it makes sense that different factors might affect different frequency ranges. This too could be much better understood with a few new more carefully devised tests.
- IMO, Eric shouldn't be singled out as one who should "go back and do some more testing". For starters, there are many other great minds at work in this field. Add to that the fact that most of them - like Eric - are involved in testing and research on a regular basis and it's kind of bad form to call him - or anyone - out as not doing enough work.
- I, for one, am not arguing. As I alluded to, I have a personal interest in the subject of absorption coefficients in general. Facts and information I provide are purely that - facts and information. When I opine or conjecture, I try to make it clear that I am doing so, so as not to confuse.
- The last statement about "a few new more carefully devised tests" is understandable. But I believe we also have a responsibility to investigate, understand, (re)interpret, and (re)apply the volumes of work - representing countless hours of labor - that have already been amassed on the subject.
> Increases in midband absorption are directly related to edge exposure and - over a limited bandwidth - could be a simple function of the ratio of exposed perimeter to area of materal, as suggested by Kuhl and Gilford. <
And please don't forget: As suggested by Ethan Winer.
As NEVER in his live suggested by Ethan Winer<SNIP>
Please see above where I've requested the citation from Ethan. I could find no technical paper references, but that doesn't mean one doesn't exist. :)
A perimeter is NOT the edge surface.
To clarify:
The perimeter is written as a measure to the power 1, an edge surface is a measure written to the power 2 or L*W.
See the mini tiny difference ????
One is called length, and the other area or surface ...... (but I agree, why discuss a difference of 1, it's close enough ..... annoying words, numbers, a dimension more or less, who cares?)
It's only a completely different concept, but all this bean counting ...... It sounds about the same ......
I think you're overreacting here. I don't think the concept of a ratio necessarily demands like units. You can have a ratio of pieces of pie to people. Why not perimeter to area? :D
Otherwise, much ado about a small thing... :?
Metaphorical:
And if there is a difference (is there?), then these "Kuhl and Gilford" guys must be wrong. As are all the other authors making the same dumb mistake.
They make no sense....... They really should all start measuring again .... with and without foil frame around the absorbers, or they are useless, University Acoustic Departments and Labs, Profs or not.
They all better check with me first .....
My investigations clearly show ..... Hoooow, I forgot: I never investigated anything, even didn't read about it, I only wrote about it. Never mind, it served and still serves it purpose.
End Metaphorical
:lol::lol::lol:
PS: This factor P/S as model parameter (or S/P depends on model) with P = 'free edge length' and S = 'area of sample':
I've no idea for sure who was first and when, but Morse and Bolt used it already in 1944.
without taking sides. if the perimeter (of some object) has a incident interface of say 3.5 inches around a perimeter of 8 feet, effectively a 2.3 sq foot presence, does this represent a material aspect to room say of 1775 cubic feet (a small room)? does this become material in if I have say 8 of these (representing 20 sq feet)? not withstanding other measurements, would someone be inclined to differentiate the acoustic response? just curious...
Um. I am not quite making out your questions from this. Could you please try to rephrase? Thanks!
Guys, some good stuff here; and I'd like to thank you ALL in advance for keeping things at least borderline CIVIL - I know firsthand how much control it sometimes takes to do this, but please do it - I'd hate to have to lock this one down for the usual reasons, and
I'M WATCHING...
Jeff,
> Starting off with insults. <
You wasted a fair amount of bandwidth criticizing my capitalization. :roll: But you were right about that, and also about ASTM being a US organization. So yesterday I changed those in both places they appear.
> I will remember this the next time you ask people to "simply point things out" to you <
That was hardly simple. But if you want a point by point discussion of whether I used a comma where there should have been a semicolon, I'm glad to oblige. I have a feeling the ol' roll-eyes smiley will get a good workout. I'll save that for a subsequent post.
> I completely ignored all the off-topic comments and insults you threw at me a few days ago <
Actually, you tossed the first grenade when you entered this thread with, "Man, this is some funny poop." Poop being the operative word since your first "point" was to criticize my using the word "convert" instead of "calculate." Sheesh.
So where are "all the insults I threw at you?"
I put that in bold because I expect an answer. Thanks in advance for answering.
> The accuracy and scientific substance of THE NUMBERS GAME has come up many times. <
You bet it has - but only by you and your friends! Every time I ask for something specific all I get are more insults. At least now you have progressed to nit-picking my capitalization.
> Being that you are not involved in math or science in any capacity <
This is the worst example of "the pot calling the kettle black" I've seen in a long time. You and your friends insult me repeatedly, and then you have the nerve to accuse me of insulting you and making off topic remarks! Unbelievable. :roll:
Here are all the insults I tossed your way in this thread:
1) "you ain't helping matters much" (in reply to your "poop" comment)
And here are all the insults thrown at me so far in this thread:
1) I do find that a bit hypocritical on your part
2) I sense more hurt feelings
3) Conclusions written by this Author are hardly related to acoustics as a science
4) The author of the "numbers game" article just publishes things, has no background or data to substantiate any of it, didn't even bother to check any literature, but still (mis)uses it to question measurement data of competing products (even based on a nonsense mathematical approach) and to enhance their own products and pseudo-objectivity (!?!).
5) in the context of THE NUMBERS GAME, "manipulated fairly" would be an oxymoron.
6) Being that you are not involved in math or science in any capacity
Most amazing of all is that you and I agree that edge surface absorption is a legitimate contributor to absorption coefficients greater than 1.0. That's the whole point of my Numbers Game article, yet you'd rather argue and call me wrong just to call me wrong. Amazing. :roll:
--Ethan
4) The author of the "numbers game" article just publishes things, has no background or data to substantiate any of it, didn't even bother to check any literature, but still (mis)uses it to question measurement data of competing products (even based on a nonsense mathematical approach) and to enhance their own products and pseudo-objectivity (!?!).
This is NOT an insult, but a dry and very accurate statement of fact, very important for readers how to rate this and put it in context.
Ethan Winer wrote:
> Increases in midband absorption are directly related to edge exposure and - over a limited bandwidth - could be a simple function of the ratio of exposed perimeter to area of materal, as suggested by Kuhl and Gilford. <
And please don't forget: As suggested by Ethan Winer.
Your own words confirm that you don't know what those authors (and all others for that matter) are talking about. And what they tell is miles away from your statements and suggestions.
They do NOT take any edge surface into acount in modeling the edge effect. What they try to define is the extension of the geometrical area (area of influence) in function of absorption en frequency.
Your explanation of the edge effect is WRONG. That's again not an insult, but a dry, very accurate statement of fact.
And by your wrong explenation, caused by your own lack of understanding and knowledge, you block people from understanding acoustic behavior in a lot of circumstances.
But I'm aware that it has no sense to discuss this any further with you, nor will you take any responsibility, and that everything will remain as is. Also clear is that most people don't mind to be misinformed, or aren't willing to do anything about it.
Jeff,
> Um, 10 m². Says so right in my post <
That was in the section after the specific statement, "midband absorption increased roughly 20-30% for each doubling of exposed edge area." You did not make it clear that the 10 m² was part of the same test.
> Theoretically, this is true. But in the contexts of acoustical treatments and the "commonly" used ASTM C423 test, the absorption coefficient can never be 0.00 and can exceed 1.00...which does not mean 100% of the sound is absorbed. <
Whatever. Since you started by agreeing, I'll take that as arguing just to argue. :roll:
Also, your comment that 0.0 is impossible is wrong. I've seen results less than zero at low frequencies.
> For normal incidence absorption coefficients, this would certainly be the case. But, again, in the contexts of acoustical treatments - almost always tested for random incidence absorption - it is not the case. <
Again you agree with me, and then argue just to argue by bringing in an unrelated issue. The basic premise as I stated it is correct, especially when you consider the target audience.
> While there is potential for confusion, numbers greater than 1.00 do not make comparisons difficult. <
And your point is? Yet again (three times in a row now) you start by agreeing with me, then nit-pick to death just to argue.
> Data manipulation is not part of the laboratory method. <
By "manipulated" I meant by vendors of acoustic treatment products. You know, companies such as Auralex who claims absorption coefficients for a standard LENRD far exceeding 1.0 at all frequencies above 100 Hz.
> The ASTM is a US-based organization. <
Yes, you are right. Thanks for that. Even though that error was totally irrelevant to the topic of discussion, it was still wrong.
> Edges are discussed in ASTM C423, Section 9. <
Yes, and I never said otherwise. However, the standard A Mounting test does indeed "overlook" the edges, and this is the most common test used by companies such as Auralex and everyone else.
> To summarize, test specimens are to be mounted "in a way that simulates actual installation." A subsequent Section states that edges of materials intended for ceiling installation (i.e., a T-bar grid) should be sealed. A good lab usually asks a client whether the edges of the test specimen should be sealed. Since the edges of wall panels are typically exposed, this is not often done for foam and fibrous panels. Since, to the best of my knowledge, the edges are rarely - if ever - sealed for wall panel tests, it is usually safe to compare the results of absorption tests, provided all other factors are equal to one's satisfaction. If there are any doubts, the manufacturer should be contacted. Section 12 of the C423 test method requires a full test report, which must include a detailed description of the exact conditions of the test specimen in the lab. <
I agree with all of that. Of course, all of that is already explained fully in The Numbers Game on the RealTraps site. See the paragraph that begins, "Note that measurements for RealTraps products are modeled after the ASTM type "J" standard..."
> The test does "ignore" the area of the exposed edges. <
Gosh, isn't that exactly what I said?
> most every absorber on the market reports absorption coefficients that omit the edge area. Thus, it is largely moot with respect to fair comparisons. <
Yes, but the main point of my article is to explain why you can get values greater than 1.0. So I see nothing wrong with my wording.
> If memory serves, 8 MiniTraps were tested in the "A" configuration ... If the additional area is included - which is not in accordance with the standard method ... 112/74 = 1.51 <
No, the MiniTraps were four inches off the floor. This is clearly stated on our site, and that is why your AbsCo calculations come out too high.
> This final sentence seems to be insinuating that there is some unfairness going on. If virtually every absorption coefficient is calculated using the method in question, then all the numbers are equally inflated. <
No, they are not equally inflated because the amount of inflation depends on the panel thickness.
> During the test, all four edges would not be exposed. <
Yes, but that too is explained clearly in the last sentence where I state, "But even when placed to form a single surface area of 8 by 8 feet, four-inch thick edges still inflate the measurements by more than 16 percent."
> thus the published numbers (not "specs," btw) <
Yet more grammatical nit-picking in lieu of having anything of substance to criticize.
> The edges did not contribute to the published "specs." They were omitted from the calculation. <
No, you're wrong. The edges do increase the absorption coefficient calculated from sabins because the sabins are higher that they would be had the edges been covered.
> The manufacturer may have its own suggestions, but the needs of the space will dictate how most acoustical panels get installed. <
Good point.
> Most acoustical professionals are well aware of the limitations of using lab test data in their models and will typically take those limitations into account when selecting acoustical treatments for a room design. <
My article is not intended for "most acoustical professionals" as you well know.
> For the devices in question, total absorption, or absorption per unit, could provide the necessary information for comparison, but would require modification to the standard test methods to accommodate. <
Yes, and that's my whole point. The data Auralex publishes for LENRDs is pure fiction for precisely the reasons I explain in my article. With published absorption coefficients equal to or greater than 1.0 at all frequencies from 100 Hz and up, a prospective customer might assume stuffing LENRDs from floor to ceiling in each of the four wall-wall corners will give an adequate amount of bass trapping at 100 hz and higher. I'm sure even you will agree this is unrealistic.
> I have mentioned (opined) in other threads that manufacturers should follow the lead of RPG and perform low frequency specific measurements on their low frequency devices. <
I have been arguing for better (more relevant) LF product testing since Day One. As I recall, it was you and your friends who argued against that, saying the existing methods are perfectly adequate. I'm glad to see I've had some positive influence on you.
> While the intent of this paragraph is understandable, the "65 percent" comment has no basis. The devices would have to be retested with the edges in question sealed in order to determine what the actual difference in absorption would be. <
Or you could just calculate it as I did.
> the last sentence here would seem to contradict claims made elsewhere in THE NUMBERS GAME. <
Such as? Please don't be like you know who, calling me wrong just to call me wrong but without further explanation.
--Ethan
> This is NOT an insult, but a dry and very accurate statement of fact, very important for readers how to rate this and put it in context. <
By that "logic" I could call you a bitter little man who has nothing of substance to offer. As long as I summarize with "This is NOT an insult, but a dry and very accurate statement of fact" nobody could accuse me of insulting you. :roll:
> This is NOT an insult, but a dry and very accurate statement of fact, very important for readers how to rate this and put it in context. <
By that "logic" I could call you a bitter little man who has nothing of substance to offer. <snip>
I did state accurate facts. This has nothing to do with "By that logic", but a plain summary of facts.
You state an opinion, meant to insult, as only pore defense against facts ...
You can't insult me.
Everytime you try you even help me.
I know that there are people who can read and see.
This is getting pathetic guys.
For the information of members who aren't informed "Lovecow" is in fact
Jeff Szymanski, Chief Engineer at Auralex. I find it interesting that he needs to use a webname. It used to be his signature but I notice he's removed that aspect.
Jeff - I've wandered through the Auralex site and I could pull you up as many times as you've tried to pull up Ethan.
here's one to start with:
you state on your site:
The best way to tighten up a room's sound and make it more soundproof in the process is to design it right, build it tight and make the partitions as dense as possible. That's where our specialized Mineral Fiber sound insulation comes in. It's WAY more dense than "the pink stuff" and is specifically designed for acoustical usage. It yields much better bass trapping, overall absorption, thermal characteristics, moisture absorption and sound transmission loss (isolation) than any other product we've found. (my emphasis.)
Auralex Mineral Fiber - values reported as octave-band absorption coefficients in accordance with ASTM C423. Mounting TypeA.
2" 0.32 0.90 1.11 1.07 1.01 1.05 NRC 1.00
for comparison:
Johns Manville 2" Spinglas Board. Type “A” Mounting Sound Absorption Coefficients* Tested in accordance with ASTM C 423-90a and ASTM E 795-83
2" - 0.38 0.93 1.10 1.07 1.07 1.07 NRC 1.05
how far did you look??
here's another one:
Floating the Walls- The studs were installed 4” from the outer walls to create dead air space between the outer and inner walls. The studs were then lined with Auralex Mineral Fiber, a specially designed acoustic insulating material. The construction of the wall surface began with using Auralex RC8™ Resilient Channel attached to the wall studs. These specially-formed metal channels are used to mount drywall as opposed to having the drywall mount directly to the studs.
why use a resilient channel when the wall has only one side of drywall? RC is typically used as a method for increasing STC when BOTH sides of a wall have drywall as it decreases sound transfer through the stud to the next drywall layer. In your case there is no drywall on the other side to transmit to, just dead airspace.
I could go on but it's not important IMO. I accept that on your site you are addressing your prospective clients who have little or NO acoustic training, just as Ethan does at his site. Therefore, let's not judge the statements made on either site as papers submitted for a University Degree.
cheers
john
For the information of members who aren't informed "Lovecow" is in fact
Jeff Szymanski, Chief Engineer at Auralex. I find it interesting that he needs to use a webname. It used to be his signature but I notice he's removed that aspect.
Not so. Been gone from there for a number of months now. Sorry I didn't inform you earlier, John. (Hence the reason my sig no longer goes into much detail.)
As for the statements you pulled, I probably didn't write them - I rarely got into web content. I did some work on the FAQs, some PDFs (most notably the "Acoustology" pieces), and some re-editing of Acoustics 101 to bring it more in line with sites like yours.
Other than that, you'll have to contact Auralex if you have beefs with their site. :)
Jeff,
> Um, 10 m². Says so right in my post <
That was in the section after the specific statement, "midband absorption increased roughly 20-30% for each doubling of exposed edge area." You did not make it clear that the 10 m² was part of the same test.
I'll try to make it clearer for you in the future.
> Theoretically, this is true. But in the contexts of acoustical treatments and the "commonly" used ASTM C423 test, the absorption coefficient can never be 0.00 and can exceed 1.00...which does not mean 100% of the sound is absorbed. <
<Sarcasm removed.>
Also, your comment that 0.0 is impossible is wrong. I've seen results less than zero at low frequencies.
Ah, yes - thanks for pointing that out. The negative coefficients you've seen are likely because something was resonating. This will increase decay. Which will cause a negative decay delta, yes. I don't think you'd ever see 0, though. (I'm thinking asymptotic, but I will think about it some more... I remember reading somewhere that the function Sabine dervied for absorption was hyperbolic. Eric - thoughts on this?)
I have also seen negative absorption when the test veered from the standard method enough that (for wont of a better expression) "the math couldn't handle it." If memory serves, that was always in the non-standard bands. This would lead to readjustment of the specimen, checking the statistics, etc. Try and remove what wasn't supposed to be there. But that was always R&D - not official tests. I don't think I've ever seen negative absorption in official tests unless something was very obviously resonating.
> For normal incidence absorption coefficients, this would certainly be the case. But, again, in the contexts of acoustical treatments - almost always tested for random incidence absorption - it is not the case. <
Again you agree with me, and then argue just to argue by bringing in an unrelated issue. The basic premise as I stated it is correct, especially when you consider the target audience.
An absorption coefficient of 0.50 from a reverb room test does not mean 50% absorption no matter who your target audience is.
> While there is potential for confusion, numbers greater than 1.00 do not make comparisons difficult. <
And your point is? Yet again (three times in a row now) you start by agreeing with me, then nit-pick to death just to argue.
Taken out of context, I'm sure you'd think that. If you'd have read the rest of it, you would have seen what I meant.
> Data manipulation is not part of the laboratory method. <
By "manipulated" I meant by vendors of acoustic treatment products. You know, companies such as Auralex who claims absorption coefficients for a standard LENRD far exceeding 1.0 at all frequencies above 100 Hz.
Auralex has a good explanation of all that in the documentation that accopmanies the official LENRD test report. It would seem to me that they did not try (and currently are not trying) to manipulate anything.
As for other vendors, I can appreciate that. Thanks for clarifying.
> The ASTM is a US-based organization. <
Yes, you are right. Thanks for that. Even though that error was totally irrelevant to the topic of discussion, it was still wrong.
Boy, you just don't like to be corrected at all, do you? :?
> Edges are discussed in ASTM C423, Section 9. <
Yes, and I never said otherwise. However, the standard A Mounting test does indeed "overlook" the edges, and this is the most common test used by companies such as Auralex and everyone else.
OK.
> To summarize, test specimens are to be mounted "in a way that simulates actual installation." A subsequent Section states that edges of materials intended for ceiling installation (i.e., a T-bar grid) should be sealed. A good lab usually asks a client whether the edges of the test specimen should be sealed. Since the edges of wall panels are typically exposed, this is not often done for foam and fibrous panels. Since, to the best of my knowledge, the edges are rarely - if ever - sealed for wall panel tests, it is usually safe to compare the results of absorption tests, provided all other factors are equal to one's satisfaction. If there are any doubts, the manufacturer should be contacted. Section 12 of the C423 test method requires a full test report, which must include a detailed description of the exact conditions of the test specimen in the lab. <
I agree with all of that. Of course, all of that is already explained fully in The Numbers Game on the RealTraps site. See the paragraph that begins, "Note that measurements for RealTraps products are modeled after the ASTM type "J" standard..."
The paragraph you cited is not under the heading THE NUMBERS GAME, which is why I probably failed to discuss it. Sorry!
As for the "J" mounting, that's fine. But then why do you have absorption coefficients in the first table on this page? You cannot calculate absorption coefficients if you've used a "J" mounting. Haven't we talked about this before?
<More sarcasm removed.>
> most every absorber on the market reports absorption coefficients that omit the edge area. Thus, it is largely moot with respect to fair comparisons. <
Yes, but the main point of my article is to explain why you can get values greater than 1.0. So I see nothing wrong with my wording.
I admit to philosophizing a bit here. Fair enough.
> If memory serves, 8 MiniTraps were tested in the "A" configuration ... If the additional area is included - which is not in accordance with the standard method ... 112/74 = 1.51 <
No, the MiniTraps were four inches off the floor. This is clearly stated on our site, and that is why your AbsCo calculations come out too high.
The table said "On Wall." I took this to mean "A" mounting. Sorry about that. Would you like me to go back and remove that section from my post? Did you do an "A" mounting test - i.e., directly on the test floor in accordance with the standards? If so, I'll gladly substitute those numbers to make my point. Or I can find numerous other products that will suffice if you'd rather I remove the MiniTraps reference. Let me know! :)
> This final sentence seems to be insinuating that there is some unfairness going on. If virtually every absorption coefficient is calculated using the method in question, then all the numbers are equally inflated. <
No, they are not equally inflated because the amount of inflation depends on the panel thickness.
I believe I included - or at least should have/tried to include - an "all other factors being equal to one's satisfaction" qualifier somewhere in there. If not:
My point about the edge effect being moot in the earlier post would assume that all other factors being considered in one's comparison are equal to one's satisfaction.
Thanks for pointing that out - it was a long post and this preview window is very small! :)
> During the test, all four edges would not be exposed. <
Yes, but that too is explained clearly in the last sentence where I state, "But even when placed to form a single surface area of 8 by 8 feet, four-inch thick edges still inflate the measurements by more than 16 percent."
Right again - and I commented on that, too.
<Snippety-snip on the ol' sarcasm.>
> The edges did not contribute to the published "specs." They were omitted from the calculation. <
No, you're wrong. The edges do increase the absorption coefficient calculated from sabins because the sabins are higher that they would be had the edges been covered.
Potentially confusing (and contradictory?) point here: If the edges are omitted in the calculations, they cannot contribute to the published absorption coefficients. They were omitted. They contributed to the measured absorption, yes. But not to the published values. The published values did not include the area of the edges in the calculation. The absorption coefficients are the absorption of the area of panels with or without the edges exposed. Since the state of the edges is in the test report, an inquiry to the manufacturer of the product/panel in question can usually clear up any questions about the state of the test specimen. Perhaps you could include some statement like this in THE NUMBERS GAME? "If you're unsure about whether the manufacturer tested the product with the edges exposed or not, contact them for a copy of their test report!"
> The manufacturer may have its own suggestions, but the needs of the space will dictate how most acoustical panels get installed. <
Good point.
Thanks!
> Most acoustical professionals are well aware of the limitations of using lab test data in their models and will typically take those limitations into account when selecting acoustical treatments for a room design. <
My article is not intended for "most acoustical professionals" as you well know.
> For the devices in question, total absorption, or absorption per unit, could provide the necessary information for comparison, but would require modification to the standard test methods to accommodate. <
Yes, and that's my whole point. The data Auralex publishes for LENRDs is pure fiction for precisely the reasons I explain in my article. With published absorption coefficients equal to or greater than 1.0 at all frequencies from 100 Hz and up, a prospective customer might assume stuffing LENRDs from floor to ceiling in each of the four wall-wall corners will give an adequate amount of bass trapping at 100 hz and higher. I'm sure even you will agree this is unrealistic.
No way. Perhaps here lies the ultimate disconnect. A room can be treated adequately above 100 Hz with devices like LENRDs. Not every room, but there are rooms where this is completely possible. It is doable and has been done. I've measured it. I've lived it.
And the most important point: In each and every instance where this was accomplished, it was accomplished without a single glance at test numbers. The numbers for LENRDs, MiniTraps, TubeTraps, 2" 703, 4" 705, and any other acoustical product one care's to consider that has been tested per the ASTM C423 (or equivalent) test method are completely meaningless in the contexts of small room acoustic design.
So all this is much ado about nothing. Truly.
> I have mentioned (opined) in other threads that manufacturers should follow the lead of RPG and perform low frequency specific measurements on their low frequency devices. <
I have been arguing for better (more relevant) LF product testing since Day One. As I recall, it was you and your friends who argued against that, saying the existing methods are perfectly adequate. I'm glad to see I've had some positive influence on you.
You have argued for better testing. We agree on this. I have been much less public about my feelings - I feel researching and thoroughly considering all the alternatives rather than blindly making up new methods is the best way to do things.
I cannot speak for others, but what I argued against is your proposed alternative testing method - i.e., corner testing per ASTM C423. I don't believe it to be a good or reliable method. I will continue to argue against it.
From the very first time I contemplated how to test a bass trap, I have sought for a better way. This seeking out of better test methods has never been influenced by you, I'm afraid. (Sorry to disappoint.)
The way I see it - and, again, much research and contemplation to back this up - the RPG method is worth it for you and other manufacturers to pursue.
> While the intent of this paragraph is understandable, the "65 percent" comment has no basis. The devices would have to be retested with the edges in question sealed in order to determine what the actual difference in absorption would be. <
Or you could just calculate it as I did.
Calculate what? A test with the edges covered was not performed. So how would you even know what to calculate? You're speculating, not calculating. (No offense intended - it is speculation.)
> the last sentence here would seem to contradict claims made elsewhere in THE NUMBERS GAME. <
Such as? Please don't be like you know who, calling me wrong just to call me wrong but without further explanation.
I thought it was obvious, but - given the length of the post - can see now that it probably wasn't. (Forest for the trees...) This statement:
THE NUMBERS GAME wrote:
The Sabin is an absolute measure of absorption, independent of surface area, and it can be used to compare any two absorbing devices directly and on equal terms.
would appear to contradict this one:
THE NUMBERS GAME wrote:
Although 1.0 is the largest legitimate value possible, you may have seen higher numbers claimed for some products. Needless to say, this causes confusion, and makes it difficult to compare published data.
Maybe contradiction is not the right word. Maybe it would be better to ask: If the absorption coefficients could cause confusion and make comparisons difficult, why not state right away that comparing sabins could be a better approach? And then explain how it can be done? I realize I might be playing "editor" here a bit more than I should (sorry, John). But, again, just trying to help. :)
You wasted a fair amount of bandwidth criticizing my capitalization. :roll: But you were right about that, and also about ASTM being a US organization. So yesterday I changed those in both places they appear.
Splendid.
> I will remember this the next time you ask people to "simply point things out" to you <
That was hardly simple. But if you want a point by point discussion of whether I used a comma where there should have been a semicolon, I'm glad to oblige. I have a feeling the ol' roll-eyes smiley will get a good workout. I'll save that for a subsequent post.
Ya know, I am just trying to help. You can either be helped, or continue to evade and divert attention. No skin off my nose. The thread'll be locked down soon enough, I suspect. (I noticed that Steve's watching... :wink: )
> I completely ignored all the off-topic comments and insults you threw at me a few days ago <
Actually, you tossed the first grenade when you entered this thread with, "Man, this is some funny poop." Poop being the operative word since your first "point" was to criticize my using the word "convert" instead of "calculate." Sheesh.
Well, I take this to mean either the word "poop" offends you, or you felt it was directed at you due to the first "point" you mentioned.
If it was the former, I apologize - I realize dirty words can offend some. I should've known better.
If it was the latter, I apologize for the misunderstanding. You see, the <dirty word> reference was to the thread in general - I found some of the posts amusing is all. My correction of your choice of words is a quirky habit I have, I'll admit. But we've been doing this a long time - surely you're used to that sort of thing from me by now, no? :)
So where are "all the insults I threw at you?"
I put that in bold because I expect an answer. Thanks in advance for answering.
Actually, you spread the lovin' pretty well: me, Auralex, ReadyTraps, and Eric. And I thought you preferred to stick to the points at hand? "Acoustics Police." You accused me of "copying" a name. (The word "Trap" is hardly proprietary and Auralex neither used the word "Real," nor the prefix "mini-".) Calling Auralex and Joel "imitators". "Rip-off." You attempted to insult either Auralex or Behringer - I don't quite understand your intentions with that weird comparison.
And your general tone and attitude suck, dude. That alone is insulting. Lighten up. I'm trying to help.
> The accuracy and scientific substance of THE NUMBERS GAME has come up many times. <
You bet it has - but only by you and your friends! Every time I ask for something specific all I get are more insults. At least now you have progressed to nit-picking my capitalization.
I think I covered the specifics pretty well. I will get to your (sometimes) sarcastic rebuttals shortly, though... <Edit: Somehow, I managed to post these replies in reverse order - see my comments in the previous post.>
> Being that you are not involved in math or science in any capacity <
This is the worst example of "the pot calling the kettle black" I've seen in a long time. You and your friends insult me repeatedly, and then you have the nerve to accuse me of insulting you and making off topic remarks! Unbelievable. :roll:
Totally not an insult. You've admitted this more than once publicly. I meant nothing by it save to repeat what you have already made well-known. Again - lighten up.
And here are all the insults thrown at me so far in this thread:
1) I do find that a bit hypocritical on your part
Statement of opinion. Apologies if you took offense.
5) in the context of THE NUMBERS GAME, "manipulated fairly" would be an oxymoron.
I thought you'd find this one funny. The whole piece is kind of a big "conspiracy theory" type jab at your rivals and competitors. I thought fair manipulation to be an oxymoron in that context. Again - apologies for the misunderstanding.
6) Being that you are not involved in math or science in any capacity
Again, totally not an insult. :arrow:LIGHTEN. UP. DUDE.
Most amazing of all is that you and I agree that edge surface absorption is a legitimate contributor to absorption coefficients greater than 1.0.
I added the emphasis and, yes, this is something I can agree with.
That's the whole point of my Numbers Game article, yet you'd rather argue and call me wrong just to call me wrong. Amazing. :roll:
That bit about why I'm "arguing": Not true. And insulting. Can I add it to the above paragraph? :)
And if that is your whole point with THE NUMBERS GAME, then I hope you can curtail some of the sarcasm so we can discuss it in more detail...
Thanks to the amazing design and concept advice from Jeff Szymanski and Jeff Hedback at Auralex Acoustics
Fair enough. Your concern was:
why use a resilient channel when the wall has only one side of drywall? RC is typically used as a method for increasing STC when BOTH sides of a wall have drywall as it decreases sound transfer through the stud to the next drywall layer. In your case there is no drywall on the other side to transmit to, just dead airspace.
AFAIK, RC has been used quite often in wall built over masonry in an attempt to increase the STC. In fact, if layers can only be added directly to the masonry (no air gap), then the use of RC (or equivalent) is necessary to prevent resonance. I believe this was our thinking when we put that wall design together. Perhaps this is overkill? Wrong? What are your thoughts? I'll try to dig up supporting test data. (In support of or not - you've piqued my curiosity now! This approach was something that was always more "gut reaction" than "it says so in Mr. So-and-so's Handbook." Now that you've questioned it, I need to know more!!! :) )
In the appplication where you used RC you were dealing with a 2" x 4" stud frame freestanding and 4" off the outer wall if the report is correct. As I said before the idea of RC is to lift the drywall off the stud to decrease sound transfer into the stud and hence through to the next drywall layer.
Recovered from web.archive.org — originally hosted at http://www.saecollege.de/reference_material/images/Wall%2012.gifIn the case of the drum room adding the RC would have increased (raised) the resonance as drywall on RC is not as rigidly attached (braced) as drywall directly attached (glued) to a stud wall, even more so when the stud wall is further strengthened with horizontal stringers at 4' spacing (a system that incidently is compuslory in my country in all stud wall constructions but is apparently is not in the US).
cheers
john
For the devices in question, total absorption, or absorption per unit, could provide the necessary information for comparison, but would require modification to the standard test methods to accommodate. <
Yes, and that's my whole point. The data Auralex publishes for LENRDs is pure fiction for precisely the reasons I explain in my article. With published absorption coefficients equal to or greater than 1.0 at all frequencies from 100 Hz and up, a prospective customer might assume stuffing LENRDs from floor to ceiling in each of the four wall-wall corners will give an adequate amount of bass trapping at 100 hz and higher. I'm sure even you will agree this is unrealistic.
Chaos as a system.
One has nothing to do with the other.
Auralex measurements as published are type A mount done in a period nobody did corner measurements, for the very simple reason that standards do not provide provisions for that.
A note was made on Auralex site to that effect.
Correct is that the measurements as are, are useless for corner mounting.
Correct is that it becomes time that Auralex provide normal corner mount measurements, because while the official report is provided, hence allowing people to see how they are measured, this data is misleading for laymen.
The added article as more recent complement to those old measurements, is just a diversion of the real thing, acceptable as substitute for a limited amount of time until others are available. Also for me they are long overdue.
But the RealTraps site has always been an example how NOT to present data.
But this whole thing has nothing to do with Ethan's response and the way he misuses it. This are complete separate topics.
It even sounds here that Ethan, since he does not agree with the current available A-mount data (which I could understand) gives himself the right to wrap this in a pseudo scientific cloth to question this data via complete non-related things, but then generally applicable for anything.
The MiniTraps in corners and on walls are as well subject to the edge effect as any foam product.
My related comments stand for 100%.
In fact in this thread chaos is used as a system.
LENRDs or whatever other corner device even when mounted from floor to ceiling and showing no edge surface whatsoever are strongly defined by the edge effect.
Finally John takes this personally in function of Ethan and start discussing Auralex.
When Auralex is wrong Auralex is wrong as well. I completely agree with that.
It's not about knowing more or less, but when things are (mis)used as a system.
It's important that laymen readers can rely on the info they get, no matter from where.
They lack the build-in warning systems from experts.
In the same manner I also hope that what I read about topics I don't know about are written by writers/companies with some ethics, just BECAUSE I lack the background to judge it.
This is what I recently said:
http://forum.studiotips.com/viewtopic.p ... ght=#28930
And Brian Ravnaas is one of the cleverest guys one find in groups. I do respect him an extreme lot.
I disrespect all nonsense used to mislead people, no matter who uses it. Because it shows disrespect for people itself.
A agree with you John, that this thread becomes pathetic. But that's related to chaos, chaos used as a system.
And, sorry Jeff, but you didn't really help to prevent it from happening.
I made a point.
I substantiated my point with measurements specific executed for this purpose.
Either I falsified my measurement data or I proved my point.
It's as simple as that.
Detailed discussions about individual bands do not alter the trend or main principle they represent.
Neither does solving the complete edge effect problem and question marks with additional measurements. Literature about it is written from 1944 - Morse and Bolt - (and maybe earlier) and is regularly studied until nowadays.
Hence nobody is dependent on my measurements alone, which is only part fitting within a much bigger whole.
Earlier: Sabine himself knew it, but I don't know exactly what he did with this knowledge. What we do know is that he didn't translated it simply to include the visible exposed surfaces, otherwise it should be common knowledge and possibly part of his formulas.
As a fun side comment. One can even wonder how he did what he did with the poor available measurement equipment (Reverb times were measured by a guy with some kind of stopwatch sitting in a box with only his head outside that box. I've recently seen a picture of that. still don't understand how this can work, but it did somehow).
Others documented it from the 1930ties (but haven't seen documents yet).
Those measurements date from long before RealTraps existed
The stupid situation occurs, that first my measurement's quality and validity are questioned (which I take personally since that goes directly to my integrity and that of the Prof. involved), then more extensive prove is demanded from me, as arguments to hide behind by a writer, who wrote an expert article and (mis)uses its related conclusions, with an extreme penetration to countless readers, based on nothing.
All literature discussing the edge effect, will contradict Ethan's approach (in that he is unique), yet rather than reading about it he continues as is. I will still see the first acoustician active in this field, who will take the EW foam corner fill calculation serious, and certainly within the suggestive context it is used.
And every argument, even the stand of the moon, will be used not to take his responsibility as a writer.
And you hardly can distinguish those points as individual autonomic events as Jeff entered his quote. Hence this is only diversion within the context of this thread.
Even top acousticians don't agree on all points in function of exact modeling, and it's a typical topic which at one point or another is studied in about any lab.
One thing they all agree on that it is NOT what Ethan says.
Not one related prediction algorithm I know off, handling this edge effect, takes edge surface into account, which while for Ethan unacceptable and incomprehensible, for me looks as normal logic. One wants to find the expansion outside the board of this area of influence, therefore one needs to know the edge length versus the surface (hence, as a poetic license one could call it a shape factor to rate how much edge is involved versus covered area). Better algorithms also try to cover for overlapping influences at different distances. They try to define limits of influence in function of frequency (wave length).
And therefore e.g. those LENRDs or chunks or whatever will show the edge effect on those vertical edges even without any edge surface, just by the difference in impedance between the absorbing and reflecting surface which scrambles that sound field based on wave acoustics acting as wave fronts. And it as well should be clear that there is a wave length relationship.
And this IS IMPORTANT to feel, even when not able to quantify it.
If I take 50% ceiling tiles away, then Ethan's approach masks that I will still keep 80% total absorption by this phenomenon, not explained by the edge surface which is even masked by the profile system.
And Ethan's approach will falsify the comparison of the edge effect of panels mounted from the wall versus against the wall.
Feeling this explains the extreme high values of all those absorbers spread over the lab, where increasing the cavity, while not increasing the edge surface, will also translate in an increased edge effect contribution.
And so on....
PS the most recent ISO standard will count the edge surface, not as a solution for the edge effect, but to make measurement results more serious if suppliers decide not to skirt the edges (bit complicated and not clear yet for all circumstances). In the US it seems that skirting is almost a sin and their it's more important due to smaller sample sizes.
Applying this should alter a LOT of published measurements in negative sense currently available on the net, including RealTraps ..... (I still need more study work to see the exact consequences, for not clear covered circumstances)
