# Confused by Rt60 (T30,T20,Topt)



## Joel-Raatz (Nov 28, 2011)

Hello,

I mesured my system, and now I have a probelm with understanding the RT60 plot.
For me there is no such Rt60 graph, only T30 and RT20 - so do I have to multiply them
by 2 or in case of RT20 by 3 to get my RT60. Thats what is writen in my acustic book.
But there must be a RT60 graph ?

Thanks for the help!

Joel


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## Skylinestar (Oct 19, 2010)

Can anyone please give a noobie guide explanation regarding reading the RT60 plot? What's Topt, EDT, T20, T30?


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## JohnM (Apr 11, 2006)

There is an explanation in the RT60 graph help. All are RT60 times (i.e. times for level to drop by 60dB) but are calculated by analysing different portions of the impulse response. REW's Topt generally gives the best result. EDT (Early Decay Time) refers specifically to the initial portion of the decay and is not directly comparable to the T20/T30/Topt measures.


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## Joel-Raatz (Nov 28, 2011)

Thanks a lot! now I got it onder:


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