MORE questions about "edge effect" absorption cont

[z60611]

Eric:

My mistake. That 1935 one was by P. E. Sabine (not Walace).

[Eric_Desart]

Eric,
So you are saying that the edges have nothing to do with increasing the absorption coefficient number when the edges are open?

A retake:

Glenn,
This feels as a trick question to me, not even sure it comes from you yourself.
I nowhere said that, and I said stuff to the contrary. How can this be a summary of what I said?

And this still does NOT mean that I confirm the EW approach, which remains wrong.


Bob
I was sure it was some minor confusion here or there.
I know your accuracy. Was just a bit fun.

Equally fun is the list of references at the end about the many studies that have been done about the changes in absorption coefficients by spreading out absorbers........

That's not quiet fair of you Bob: calculating the edge surface is rather difficult, hence it's logical that so many top experts studied the problem for over 70 years.
But that will all change now since the modern edge surface™ method is published.
Thanks to this new method we can even convert A-Mount measurements we don't like, of annoying competitors, to more acceptable Corner Mount measurements. Something none of the previous models could accomplish.


ASTM refers to some of those Authors to be found in Bob's link, in order to explain why values higher than 1 can occur and why they don't correct those absorption values, but leave them as is:
[quote="ASTM C 423, using as "alibi" following references not to use the edge surface, known by Ethan Winer having a copy, "]5.Chrisler,V.,“Dependence of Sound Absorption Upon the Area and Distribution of the Absorbent Material, ”Journal of Research, National Bureau off Standards, Vol13, 1934, p.169 :Northwood, T.D., Grisaru, M.T., and Medcof,M.A.,“ Absorption of Sound by a Strip of Absorptive Material in a Diffuse SoundField, ”Journal of the Acoustical Society of America, Vol31, 1959, p.595: and Northwood, T.D., “Absorption of Diffuse Sound by a Strip or Rectangular Patch of Absorptive Material,” Journal of the Acoustical Society of America, Vol35, 1963, p.1173.[/quote]
Translated by the Author of the new edge surface™ method as:

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.

This is not the exception but the standard way this author writes. He just writes wat he wants his readers to believe, knowing most are laymen anyhow.

[myfipie]

Eric,

"Glenn, I did not say they those edges have no effect with or without frame. Absorption will have. This DOES NOT MEAN THAT YOU JUST CAN PUT AN OVERSIMPLIFIED INCORRECT ALTERNATIVE INSTEAD, as this document shows."

Ok no problem, I still need to read over a few more time what you wrote but it makes sense to me. I figured you did not say that, but then again there just seemed to be A LOT said in the thread.

"This feels as a trick question to me, not even sure it comes from you yourself."

Eric I like you, but DO NOT ATTACK ME. If you would rather I do not ask you a question then I will not. I think for myself. OK? Sorry if that seems harsh but this is not the first time you have come back at me saying something or questioning my intentions with you.

Bob,

wow that was very well said, what ever I did not understand from Eric you pretty much cleared it up. Glad to have guys like you around.

Glenn

[myfipie]

Ok Eric just read through the whole post and now understand.. I can not open that doc that you gave but I think I understand what you are getting at. You did point out one thing that did make me ask my question.



"Your Tri-corners will show edge effect absorption on those sharp edges as well as on the junction wool/closed top. "



Is there any way to tell how much is edges (sides as per EW) and how much of it is Edge Diffraction.

Glenn

[John Sayers]

I can not open that doc that you gave

there was problem with a .doc; on the end of the filename.

here it is without it.

[myfipie]

It must be my stupid computer. It just keeps crashing when I try to open the file..

Glenn

[z60611]

materials tested to ASTM standards in different facilities can be compared with confidence.

I would have added the word 'limit' after the word 'confidence'.

[Eric_Desart]

Ok Eric just read through the whole post and now understand.. I can not open that doc that you gave but I think I understand what you are getting at. You did point out one thing that did make me ask my question.

"Your Tri-corners will show edge effect absorption on those sharp edges as well as on the junction wool/closed top. "

Is there any way to tell how much is edges (sides as per EW) and how much of it is Edge Diffraction.

Glenn

Glenn,

To be honest: NO.
It's already complicated for standard stuff, But you will have edge effect on all 4 front edges (the bottom I can't rate very well, my belly fails).
And please. Stop separating this as such. This is frequency related. One effect will be more related to other ranges as the other. It's not x% for this and y% for that.

Try to see it this way: Once there is a difference in impedance, meaning see a wave as a front also having a width, and you absorb part of it (block it) and the rest not, you disturb that wave which will cause such edge effect.

See that wave as an elastic front where all those air particles are elastically connected with one another. Once you grab part of that wave you also influence the rest of it.

With corners it's even more unclear with this gradual thickness of the material and corner absorption question marks in itself.

Hence if you make your corner absorber smaller you get
1) Relative more edge effect which will increase absorption coefficients since that's calculated per surface unit.
2) some wave length related phenomenon which will make them low frequent somewhat worse. (logical: smaller absorber)

Basically with discrete absorbing objects you can f*ck up the absorption coefficients just by making them smaller.
That's why the standard forbids to use absorption coefficients for such objects.

Towards the others:
Some suppliers now agreed that they should respect the standard more, and will adjust there data to it. This includes GIK (I hope this will become true).

And Fun:
Basically this what is systematically be abused on the RealTraps site for years already. Which is why it became difficult for others to comply with the standards.
One will notice that the method introduced by RealTraps, AGAINST the stipulations of the standards, now starts bringing themselves in trouble.

You will notice that the REAL LENRDs are ACCIDENTALLY excluded from the absorption coefficient data table.
As per the by RealTraps introduced wrong method (sold as a standard method to convert between sabins and coefficients, as long as useful) those LENRDs become DAMNED GOOD absorbers compared to the MiniTraps in corners, when expressed as per the so-called standard method in absorption coefficients.
The result: that column lacks in the table (who from those laymen will notice anyhow ....?????).
Just apply the so-called standard conversion yourself and you'll notice WHY they aren't ACCIDENTALLY in that table (being much smaller units).
http://www.realtraps.com/data.htm

And if someone thinks this is personal: Other companies have agreed now to respect the standard (working on that), and a US lab responsible, told that he will check the things brought to his attention, in order to prevent lab values to be abused for commercial purposes.

I'm not for nothing referred to in this thread as a:

bitter little man who has nothing of substance to offer

And I have nothing with foam or whatever other absorber. I hardly ever used foam (expressed in%). I'm a typical mineral wool user.
I do respect Jeff a lot, as a person, not because he's or was part of Auralex, because I have some question marks to their approach as well.
And I can even imagine that as an acoustician, within his professional responsibilities, things weren't always that easy for Jeff as well.



PRACTICAL (Word Doc. or other downloads)
If you have trouble downloading a document in a forum like this, or other sources try the following:

1) Select the download link.
2) Right-Click this link.
3) Press command: Save target as ....
Only then open it.

This should do the trick.

Best regards
Eric

PS: John thanks for uploading that document here.

[Ethan Winer]

Guys,

Over the past few days I have written several pages full of words defending myself against Eric and Jeff's ongoing and wholly unjustified accusations. It's clear to me that whenever I'm around Eric loses whatever objectivity he might normally have. And Jeff continues to behave like a disgruntled competitor whether he still works for Auralex or not. But there simply was no way to phrase the words without myself being perceived as insulting because everything they wrote was insulting and unprofessional first. But now, with Eric's latest post, it's all crystal clear.

In response to the very direct question "Is there any way to tell how much is edges (sides as per EW) and how much of it is Edge Diffraction," Eric wrote:

> To be honest: NO <

Well, then there you have it. Eric, you now admit you don't know what proportion of the increased absorption is due to simple edge exposure and what proportion is due to diffraction. So how can you argue so vehemently (and venomously) against me? For a man who claims to be dedicated to science above all else, you have now revealed your biased agenda. As if it wasn't obvious already!

> You will notice that the REAL LENRDs are ACCIDENTALLY excluded from the absorption coefficient data table ... LENRDs become DAMNED GOOD absorbers compared to the MiniTraps in corners, when expressed as per the so-called standard method in absorption coefficients. <

WTF?! Are you joking, or smoking crack again? First, I purposely did not calculate absorption coefficients for the LENRD data we measured at IBM for the very reason you criticize me repeatedly! It is impossible to fairly portray a triangle shaped absorber, where only one face will be exposed in use, using the standard calculations. Further, if you look at the sabins data for LENRDs - which is what really matters - and conclude they are "DAMNED GOOD" when compared to a MiniTrap at bass frequencies, you are even more foolish and biased than I thought.

Folks, look at this graph showing three absorbers measured in corners at IBM's lab, and let us know if you agree that RealTraps needs to "hide" the comparison of LENRDs to MiniTraps:



All three products claim to be bass traps, so the range from around 100 Hz and lower is most relevent. More to the point, this is exactly why the standard tests are irrelevant for corner bass traps. Whenever I have suggested better testing is needed, Eric has stated over and over that the regular C-423 test is all that's needed. However, the sabins graph above shows the true comparison between a LENRD and a MiniTrap because it shows how much each device actually absorbs (normalized to four feet length). It also shows yet again that Foam By Mail is a fraud, but that's another story.

If a C-423 test makes a LENRD look closer to a MiniTrap, that proves MY point, not Eric's!

> ... Auralex, because I have some question marks to their approach as well. <

Then why don't you go pester Auralex? I've never seen you harrass Foam By Mail either. Why not? While you're at it, please go after all the companies who show no data at all, expecting customers to simply believe their claims. Or might that harm some people you're friends with? I can think of quite a few companies that deserve your "attention" a lot more than me.

As for Jeff and "J" mounting:

> You cannot calculate absorption coefficients if you've used a "J" mounting <

Where in the ASTM C-423 or E-795 specs is that stated? Regardless, this is explained on our site to my satisfaction, and apparently to the satisfaction of several thousand RealTraps customers, many of whom are a lot more savvy than you give them credit for.

My company's products are meant to be mounted off the wall, straddling a corner, or hung a few inches below a ceiling. This is an inherent benefit - a huge feature compared to all bass traps that came before. For me to not tout that benefit for its very real advantage would be foolish. In your perfect world there would be little distinction between four inches of Auralex foam and a MondoTrap. I'm sure even you will agree that a MondoTrap straddling a corner far surpasses four inches of Auralex foam slapped on a wall in every way one could possibly assess.

More to the point, using absorption coefficients for many acoustic panels, and especially for corner bass traps, is fundamentally flawed because that doesn't take into account the total absorption of the device. With A mounting tests, a bass trap only 6 inches square will measure the exact same absorption as a good bass trap like the ones I sell. And as Eric pointed out (thanks Eric!) that method makes a LENRD seem on paper as effective as a MiniTrap. If only! So this is one more reason that 1) Sabins are more valuable than absorption coefficients, and 2) a more relevant way to assess corner bass traps is badly needed.

To hear your one-sided arguing ("You have been given evidence time and time again, over and over, ad infinitum") you ignore what I have explained to you time and time again, over and over, ad infinitum. You disagree just to disagree and, apparently out of a misguided loyalty to Auralex, join Eric in his failed attempts to defame me and my company. Well it ain't working pal. The entire audio community knows that RealTraps makes some of the best acoustic treatment available at any price, and our client list reflects that.

The bottom line for me is the data Auralex publishes for their LENRDs. As long as they continue to spec LENRDs having an absorption coefficient of 1.24 at 125 Hz - and do so with a straight face - I have no problem specifying my traps - honestly - using "J" mounting. At least with my traps, customers really do get what they pay for and what I claim.

--Ethan

[Eric_Desart]

To all,

If anyone wants me to reply to Ethan’s message, please tell me.

Otherwise I stop this.

I think the guys who read and see and want to know, know that I'm careful to be exact.
If with this large amount of energy I could help to open some eyes a bit, it was worth it.

I know I never in my live will convince Ethan from anything. The only changes he ever introduced (after incredible amounts of energy of others and me) is after being forced since those things started to become too obvious and turning against him. Hence those changes were ONLY made in self-interest.
I can write a book about this.

What I find important is that people aren't misinformed.
People are important to me, and mostly the people relying on honest info to make their dreams come true.

I stand behind any word I said for 100%

WTF?! Are you joking, or smoking crack again? First, I purposely did not calculate absorption coefficients for the LENRD data we measured at IBM for the very reason you criticize me repeatedly!

Ethan there is not ONE living soul on the face of this earth who believes, that to please ME, you wittingly did not show that ONE single measurement as absorption coefficients in that table, while leaving all others serving your purpose.
I invite the others to try it and conclude for themselves.
I'm glad for the way you present that here, which can't be more transparent and shows what truth really means to you.


And I'm PROUD that I told Glenn:
> To be honest: NO <
Which is what makes me an honest man with a scientific attitude AND respect for people.

It also points to related knowledge, not ignorance.
Not recognizing this tells about Ethan, not me, who needs such cheap approach.


Warm regards to all, except Ethan.

To Jeff: It's up to you, Ethan wants you to go in detail allowing to diffuse/divert the thread again.

[myfipie]

Well needless to say I did learn a lot from this thread, Eric I thank you for your reply.

Ethan,

"To be honest: NO.
It's already complicated for standard stuff, But you will have edge effect on all 4 front edges (the bottom I can't rate very well, my belly fails).
And please. Stop separating this as such. This is frequency related. One effect will be more related to other ranges as the other. It's not x% for this and y% for that. "

I think what he is getting at is you may want to put in your "numbers game" a part about it is not just all edges.

Ok I think I have caused enough trouble for one day.

Glenn

[myfipie]

One thing I did what to point out.

>Some suppliers now agreed that they should respect the standard more, and will adjust there data to it. This includes GIK (I hope this will become true).<

As you saw on our new Tri Traps I just put the PDF from the lab. I think in the future that is how we are going to deal with this (I think). Just put the lab report up. That way there is no question..

Glenn

[John Sayers]

Ok - I'm going to close this down now. Everyone has had their say fairly and squarely - it's up to the reader to draw their own conclusions.

thankyou all for your participation.


cheers
john