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In situ absorption coefficient
PostPosted: Thu Mar 08, 2012 1:42 pm Reply with quote
kudzudav
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Joined: 21 Jul 2009
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Location: oxford, ms




EASERA users
I have managed the procedure to find the "reflection factor" in dB via the procedure in the EASERA manual.
My difficulty is in converting this to a absorption coefficient-
I am familiar with the impedance method, and there is some interesting information in Robinson and Xiang, "On the subtraction method for in-situ reflection and diffusion coefficient measurements", but I am at a loss looking at the statement, "More sensible is the representation of the reflection factor r in octaves or third octaves, because with these such errors are smoothed out. The absorption coefficient can be calculated by means of the formula alpha = 1 - |r^2|."

i.e.

alpha = 1-|(-10dB)^2|= -99

any suggestions? I assume I have missed something here.
thanks
Dave


Last edited by kudzudav on Thu Mar 08, 2012 2:01 pm; edited 2 times in total

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PostPosted: Fri Mar 09, 2012 5:05 am Reply with quote
Bruce
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Dave,

Have a look at my ASA Paper for some additional help. See pages 6-7.

Bruce


Last edited by Bruce on Tue Aug 09, 2022 2:45 pm; edited 1 time in total

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PostPosted: Fri Mar 09, 2012 4:17 pm Reply with quote
kudzudav
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Joined: 21 Jul 2009
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Location: oxford, ms




thank you Bruce
Is there a specific window function that is used?
I was trying to chop off the data without a function but I was unclear on windowing without processing

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PostPosted: Fri Mar 09, 2012 4:27 pm Reply with quote
Bruce
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Probably Blackman, as that is the default.

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