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EYES - Local Decay Time
PostPosted: Thu Jun 07, 2007 3:18 am Reply with quote
kfairbairn
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Joined: 07 Jun 2007
Posts: 1




I am having trouble with Local Decay Time. It seems that the greater the order and greater the time i set the LDT just gets longer and longer without converging. However using a low order and a short time i get results closer to what i expect. This indicates to me that there must be balance struck and better resolution does not necesarily mean better, or accurate results. Iv'e observed the same with AURA.
What is happening here?

Ken Fairbairn
Acoustic Engineer
Norman Disney & Young
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PostPosted: Fri Jun 08, 2007 3:22 pm Reply with quote
Stefan
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Joined: 19 Apr 2005
Posts: 167
Location: Berlin, Germany




Hi Ken,

this sounds like a two-fold problem.

On the one hand you should always choose the cutoff time at least of approximately the same length as the Eyring RT. Experimental results show that in many cases 75% of the Eyring RT suffice for conventional rooms. Of course this does not work in rooms with strong flutter echoes, double-slope behavior or similar phenomena. In such cases the concept of the RT becomes questionable anyway. (For Local Decay Time it should also be denoted that here scattering is not taken into account, as this is not an AURA function.)

On the other hand the particle number / resolution should be chosen carefully. This point was greatly improved with EASE 4.2 / AURA. But it is still true that you need to increase the resolution (for all other parameters fixed!) as long as you see the results change. Only when they stabilize the resolution is high enough, though sometimes you may want to do a second run to confirm.

Please also see this FAQ:
http://www.auralisation.de/faq/faq.php?cat=general&readit=general41#general41

If you are still doubting the results, please send us the project in question.

Stefan
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