AFMG Network
Forums for AFMG Software
AFMG Network Forum Index -> EASERA - Discussion -> In situ absorption coefficient
Post new topic  Reply to topic View previous topic :: View next topic 
In situ absorption coefficient
PostPosted: Thu Mar 08, 2012 1:42 pm Reply with quote
kudzudav
Member
 
Joined: 21 Jul 2009
Posts: 7
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

_________________
dave
View user's profile Send private message Send e-mail Visit poster's website
PostPosted: Fri Mar 09, 2012 5:05 am Reply with quote
Bruce
Member
 
Joined: 19 Apr 2005
Posts: 425
Location: Minneapolis, MN, USA




Dave,

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

Bruce

_________________
Best Regards,
Bruce C. Olson
View user's profile Send private message Send e-mail Visit poster's website
PostPosted: Fri Mar 09, 2012 4:17 pm Reply with quote
kudzudav
Member
 
Joined: 21 Jul 2009
Posts: 7
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

_________________
dave
View user's profile Send private message Send e-mail Visit poster's website
PostPosted: Fri Mar 09, 2012 4:27 pm Reply with quote
Bruce
Member
 
Joined: 19 Apr 2005
Posts: 425
Location: Minneapolis, MN, USA




Probably Blackman, as that is the default.

_________________
Best Regards,
Bruce C. Olson
View user's profile Send private message Send e-mail Visit poster's website
In situ absorption coefficient
AFMG Network Forum Index -> EASERA - Discussion
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
All times are GMT  
Page 1 of 1  

  
  
 Post new topic  Reply to topic  


Powered by phpBB © 2001-2003 phpBB Group
Theme created by Vjacheslav Trushkin
Variation by CodeWeavers