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Author Topic: Lets talk Absorption and Scattering Data in simulation programs  (Read 2834 times)

Ron Sauro

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Lets talk Absorption and Scattering Data in simulation programs
« on: January 11, 2012, 12:34:51 pm »

I do not come to this forum very often because of lack of time....but I read some of the topic titles and saw a few I really want to comment on that are very old.

Many of you know me ads most, probably do not. If you do not like what I say or you do does not mean a lot to me but I think the truth needs to be out in this industry.

Absorption coefficients that are published are in "most" cases incorrect by up to 60% or more.

Scattering information also leaves a lot to be desired as well as most "fixes" to the data.

The way scattering information is used in simulation programs is as another" absorption coefficient".

People who tell you to "add" numbers to the scattering numbers in databases are "flat out wrong".

The recent research on this indicate that "scattering" IS another form of absorption... thus increasing the absorption coefficient.

In fact, The shape of the absorption in most cases increases the absorption of the material even when the area remains the same.... THUS the numbers you have ONLY apply to the actual sample tested and cannot be extrapolated for other shapes and areas.

If interested in the researchgo to www.nwaalabs.com and download the papers on the front page.

Thr reason items like geometric (diffusion) devices do not have a scattering coefficients is because of what scattering is.

Geometric devices CANNOT be assigned a scattering number because the are NOT scatterers. They are specular reflection devices and CAN be modeled in the simulation programs and should be by using things like groups or objects.

These can then be ignored when the lower frequency limits of the device is reached. The LF limit is based on the smallest size of the device.

If interested in getting more info please email me or call me at audio_ron@msn.com or phone is 253-973-1018.
Ron Sauro
NWAA Labs, Inc




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Brad Weber

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Re: Lets talk Absorption and Scattering Data in simulation programs
« Reply #1 on: January 11, 2012, 06:20:14 pm »

Hey Ron!  Add to your comments the differences between absorption coefficients in a reverberant field as in traditional testing versus those obtained with a directional source, especially at shallow angles of incidence.  This can be rather relevant to audio as people are often applying absorption to try to impact the sound from a directional source such as a speaker.

My simplified analogy is to think of a piece of pegboard or perforated metal.  Looked at perpendicular to the surface not only do you see the entire face area but you also see significant open area.  But looked at at a shallow or glancing angle and that same thing appears as a smaller, almost solid surface.  That can become relevant with directional sound sources and some forms of absorption.
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Ron Sauro

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Re: Lets talk Absorption and Scattering Data in simulation programs
« Reply #2 on: January 13, 2012, 08:45:47 am »

Hey Ron!  Add to your comments the differences between absorption coefficients in a reverberant field as in traditional testing versus those obtained with a directional source, especially at shallow angles of incidence.  This can be rather relevant to audio as people are often applying absorption to try to impact the sound from a directional source such as a speaker.

My simplified analogy is to think of a piece of pegboard or perforated metal.  Looked at perpendicular to the surface not only do you see the entire face area but you also see significant open area.  But looked at at a shallow or glancing angle and that same thing appears as a smaller, almost solid surface.  That can become relevant with directional sound sources and some forms of absorption.

Brad,  Agreed.... Part of this is covered I think in the scattering function ....but there are several effeorts to revise many of the standards in these areas but being standarss groups it takes significant time to get this accomplished... There is third version of this problem also and that is corfficients established by the Impedance tube methods also
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chuck clark

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Re: Lets talk Absorption and Scattering Data in simulation programs
« Reply #3 on: January 21, 2012, 10:59:31 am »

Any improvements are welcome as many of us have been instinctively aware that reality is much more complex than has been allowed for to date.
A clarification of the difference between scattering and spectral reflection would be enlightening for starters.
Chuck
PS: I would think that Architects and installers of spaces where there will be music or announcements should be required to have some sort of acoustics 101 certification.
The Greeks invented amphitheaters some 2000 years before our Lord was born, ...you'd think a driffting clue would have hit the average club owner by now. How many venues will open this year with little or NO consideration given to acoustics!? It is appalling! Thank you!
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Ivan Beaver

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Re: Lets talk Absorption and Scattering Data in simulation programs
« Reply #4 on: January 21, 2012, 12:16:46 pm »

Any improvements are welcome as many of us have been instinctively aware that reality is much more complex than has been allowed for to date.
A clarification of the difference between scattering and spectral reflection would be enlightening for starters.
Chuck
PS: I would think that Architects and installers of spaces where there will be music or announcements should be required to have some sort of acoustics 101 certification.
The Greeks invented amphitheaters some 2000 years before our Lord was born, ...you'd think a driffting clue would have hit the average club owner by now. How many venues will open this year with little or NO consideration given to acoustics!? It is appalling! Thank you!
Agreed!  It is amazing the rroms that are "designed" for everything EXCEPT what the intended usage is.

They call them "AUDItoriums" (as in audio) for a reason.  NOT VISItoriums-as in visual.

The old saying goes  "when do architect students get their sleep?  During the acoustics classes".

Who care about acoustics-just put some speakers in there and it will be fine.   Yeah right.

You can't just "fix it" that easy.

Of course certificiation would put a lot of designers/contractors out of business.  I would argue that most of the people in the audio business don't even understand the very basics of audio/acoustics.

But as long as people hire people who don't even have a business license-how are you going to make sure they are certified?
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A complex question is easily answered by a simple-easy to understand WRONG answer!

Ivan Beaver
Danley Sound Labs

PHYSICS- NOT FADS!

Charlie Zureki

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Re: Lets talk Absorption and Scattering Data in simulation programs
« Reply #5 on: January 22, 2012, 07:53:53 pm »

Agreed!  It is amazing the rroms that are "designed" for everything EXCEPT what the intended usage is.

They call them "AUDItoriums" (as in audio) for a reason.  NOT VISItoriums-as in visual.

The old saying goes  "when do architect students get their sleep?  During the acoustics classes".


  Hello,

  while I agree with the general perception that many, if not, most all venues are not designed for music performances as  well as they should be, or could be...we all know that there are  trade-offs, not only in the acoustics, but time and costs of completing a project.

   I would never expect an Engineering Company, or even an Architect to approach building a Concert venue with the same expertise as an Acoustician could lend. (or even the additional input of a modern day, Concert Production Manager/Stage Manager for other ease of use).

    There are Engineering Companies that have on staff,(or contract) well know Acousticians that help with the Design and Architecture of Concert Venues...but for those businesses whom budget the additional costs. 

  Sure, many (if not all) Universities require some basic Acoustic(s) classes for their Engineers and Architect's Graduate requirements, but, as I've said, pretty basic classes and old theories, old standards and old precepts.  These classes are more often geared to ambient office levels, etc...

   The newer venue designs must take into consideration highly amplified music, sub frequencies, etc.. and less dependence on "natural" level generation of instruments and voices.

   The information is available ... only now, it's a matter of budgets.

   Hammer
   

 

   
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Re: Lets talk Absorption and Scattering Data in simulation programs
« Reply #5 on: January 22, 2012, 07:53:53 pm »


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