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Adding Multiple Absorption Coefficients



 
 
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  #1  
Old November 9th 19, 07:29 PM posted to rec.audio.pro
Sean B
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Posts: 28
Default Adding Multiple Absorption Coefficients

Hello,

So let's say I have two different acoustic absorbers covering most of the area of a room, say a bass absorber and a higher broadband absorber. They cross over at around 250 Hz. If both have a 0.5 absorption coefficient at 250 Hz, how do I calculate a total absorption figure for both acting at the same time?



Thanks,

Sean B
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  #2  
Old November 9th 19, 11:17 PM posted to rec.audio.pro
Scott Dorsey
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Posts: 16,650
Default Adding Multiple Absorption Coefficients

Sean B > wrote:
>
>So let's say I have two different acoustic absorbers covering most of the a=
>rea of a room, say a bass absorber and a higher broadband absorber. They cr=
>oss over at around 250 Hz. If both have a 0.5 absorption coefficient at 25=
>0 Hz, how do I calculate a total absorption figure for both acting at the s=
>ame time?


A square foot of a thing with a 0.5 absorption coefficient has the same
effectiveness as half a square feet of open window (which has an effectiveness
of 1.0). If you have a thing with a 0.25 absorption coefficient, you will
need four square feet of it to get the same effectiveness as a square foot
of open window.

Multiply the absorption coefficient of all the materials in the room by the
area of each of those materials, sum them up and get the total room absorption.
In a larger room you can plug this into the sabine equation and get the
reverb time of the room. In a smaller room where you don't care about the
total reverb time so much as specific room resonances, it's a little harder
but the relevant equations are in the F. Alton Everest book on small studio
acoustics.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."
  #3  
Old November 10th 19, 01:36 AM posted to rec.audio.pro
Phil Allison[_4_]
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Posts: 450
Default Adding Multiple Absorption Coefficients

Sean B wrote:

-------------
>
>
> So let's say I have two different acoustic absorbers covering most of the area of a room,


** What area is that?

All six surfaces with two independent absorbers ?

Not very realistic.


say a bass absorber and a higher broadband absorber. They cross over at around 250 Hz. If both have a 0.5 absorption coefficient at 250 Hz, how do I calculate a total absorption figure for both acting at the same time?
>


** The figures applies to the absorbers, not the room.

Nothing changes if one sits over the other.



...... Phil

 




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