Sound Absorption and Decibel Drop

[Vipul Acharya]

I have sound absorption coefficients for a material that was obtained through testing. I have the sound absorption coefficients at various frequencies as well as overall NRC, SAA and αw.

I would like to be able to translate this to a decibel drop. How many decibels will be reduced with this material. I found an equation

d = decibel drop = -20log[sub]10[/sub](1-C) where C is the (I think) the sound absorption coefficient.

I think I would just use that equation at each frequency to determine the decibel drop to be expected at that frequency?
I could use that equation with the overall NRC, SAA or αw to give an overall general sense of the expected decibel drop?
What about if my sound absorption is 1 (or greater). Would that really mean all the noise at that frequency would be eliminated?

I do understand that it only applies to sound that actually hits the material (which wouldn't be all of the sound).

Thanks in advance.

 

[Tmoose]

Lining a silencer or return air duct?
Quieting or improving the acoustics of a reverberant room ?

 

[hacksaw]

C is the ratio of of the power absorbed relative to the incident power.
The absorbed power wont exceed the incoming power.

Be sure you understand what decibels you are talking about, power db or amplitude db of the pressure pressure levels. You are showing the amplitude db in you equation.