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Reverberation paper
Old 3 days ago
  #1
Gear Maniac
 

Reverberation paper

I didn't know it, maybe others do. And maybe some people understand it.
Attached Files
Old 3 days ago
  #2
Gear Addict
 

I'll have a crack.

I think he's saying that Sabine used too many incorrect assumptions when he originated the concepts and theory behind "REVERBERATION TIME". Acousticians have always known this, however, the paper implies that all of the workarounds to fix up the Sabine formula (RT = 0.16*V/Absorption) are still using the incorrect assumptions (Eyring's attempt, etc and even all of the ray tracing software available now).

Sabine's theory can only apply above the Schroeder frequency for the room anyway. Below that, the room response is driven entirely by room resonances which are discrete and don't overlap much unless there is significant room damping (absorption) at those frequencies.

Concludes that accurate RT predictions cannot be made unless the assumptions underlying the prediction method are accurate. So, "RT can be properly calculated from the modal decay constant, based on spherical sound reflection factors [not plane wave propagation], surface impedances, pressure summation and edge diffraction effects."
Old 3 days ago
  #3
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avare's Avatar
 

Thank you Bert.
Old 3 days ago
  #4
Lives for gear
 

Thanks Bert! Interesting... I think.... but I didn't get what the conclusion was supposed to be, other than "more research is needed"...

- Stuart -
Old 3 days ago
  #5
Gear Maniac
 

Quote:
Originally Posted by Soundman2020 View Post
Thanks Bert! Interesting... I think.... but I didn't get what the conclusion was supposed to be, other than "more research is needed"...

- Stuart -


I find the analysis of RT as a statistic vs a wave phenomenon interesting.
Eric made me aware of the problems of measuring RT in room modes, differences in comparable situations in different labs and how to consider absorbing materials a long time ago, here it is repeated and some math is provided.
You can not just measure RT under the Schroeder frequency, boys and girls, not even when you're possessed by the Syndrom of Audiophile.

For the rest I guess they try to sell that piece of software
Old 3 days ago
  #6
Lives for gear
 

Quote:
You can not just measure RT under the Schroeder frequency, boys and girls, not even when you're possessed by the Syndrom of Audiophile.
+1
Key statement!

To me, it's still curious how it is that a lot of people want to talk about the RT60 time of their 8 foot by 10 foot studio... "decay times" would be a more appropriate term. Not RT60.

Perhaps just as curios are those who measure "RT60" at the mix position, then conclude that this is the RT60 number for the entire studio, no matter where you measure...

- Stuart -
Old 3 days ago
  #7
Lives for gear
People measures the RT60 because the definition is misunderstood and some pros continue to use. They do not make any difference between the concert hall, meeting room and the small room.

Definition: Antonio Fischetti in his book "Initiation à l'acoustique : Cours et exercices" / "Initiation to acoustics: Courses and exercises" describe the RT60 as a room property and write "a room property does not change with the mic position changing".


Last year i readed the testimonial of an audiophile who wished to treat his room. He hired a pro and this pro made a rt60 report at 1/3 octave.
Old 3 days ago
  #8
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avare's Avatar
 

Quote:
Originally Posted by Soundman2020 View Post
+1
Key statement!

To me, it's still curious how it is that a lot of people want to talk about the RT60 time of their 8 foot by 10 foot studio... "decay times" would be a more appropriate term. Not RT60.
What is consistent with that is that EVERY serious studio designer and acoustician knows there is no reverberant field in such spaces and the more term and metric would be decay rate but blithely continue using reverb time as the name,

Now if we (here on GS) would use flush mounted instead of the architecturally wrong soffit mounted. I am not going to write anything about phase being used for polarity. Anyone have some good soundproofing foam?
Old 3 days ago
  #9
Gear Maniac
 

Quote:
Originally Posted by dinococcus View Post
People measures the RT60 because the definition is misunderstood and some pros continue to use. They do not make any difference between the concert hall, meeting room and the small room.

Definition: Antonio Fischetti in his book "Initiation à l'acoustique : Cours et exercices" / "Initiation to acoustics: Courses and exercises" describe the RT60 as a room property and write "a room property does not change with the mic position changing".


Last year i readed the testimonial of an audiophile who wished to treat his room. He hired a pro and this pro made a rt60 report at 1/3 octave.
Over here the same, 'pro's' making fist thick reports filled with RT60 measurements in audiophile's listening rooms and no useful data in sight.
And then the stereo image is distorted and the pro tells the client to solve that problem with the balance knob until he has treated the room with 1000 diffusers.
And when the client got suspicious and asked me I found there was a mid speaker replaced (€ 1500,-) and the guy had the fase (Andre ) connected wrong.

Tragic is these charlatans make more money than honest Bertje :-).
Old 3 days ago
  #10
Lives for gear
the honest Bertje should use this

http://www.6moons.com/audioreviews/a...esonators.html

http://www.6moons.com/audioreviews/a...em4/sugar.html

"Final comments & suggestions: The sugar cube noise filters can transform any room's acoustics and are indispensable for any serious music lover."

but you and pros on GS have old acoustic conceptions
Old 2 days ago
  #11
Lives for gear
 

Quote:
"Final comments & suggestions: The sugar cube noise filters can transform any room's acoustics and are indispensable for any serious music lover."
The sad thing is, I'll bet a LOT of people fall for that, and actually buy those things! Then manage to convince themselves that the room sounds much better... If only they knew that the cubes would work MUCH effectively, if you carefully balance them on just one corner . . . They are no good sitting down flat...

There's a saying that goes something like: "There's a fool born every minute".... and I'm pretty sure most of them end up years later as audiophiles... Or maybe that should be "audiophools"...

Sugar cubes and tiny brass bowls indeed...

- Stuart -
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