insulation coefficients

[stuckatwork]

Hey,
I have a qusetion about sound absorption coefficients. I'm looking at the Owens Corning site and I see some of the coefficients are over 1.00:

http://www.owenscorning.com/comminsul/d ... Series.pdf

It is my understanding that a coefficient of 1.00 would be 100% absorption of a particular frequency. Some of the coefficients, such as the plain 703 @ 500hz is 1.14. Maybe I don't have a very good understanding of what these coefficients mean but can someone please explain to me how a material can absorb 114% of a frequency?

Thanks,
Jon

[John Sayers]

Jon - I've seen this answered somewhere, maybe by Eric at Yahoo. I remember it had something to do with Edge effects or sumthin.

Sorry I can't answer it further.

cheers
john

[Ethan Winer]

Jon,

> can someone please explain to me how a material can absorb 114% of a frequency? <

As John said it's due primarily to edge effects. And those can seriously skew the results! I just wrote a very detailed description of this exact issue as a new sidebar for my Acoustics FAQ, here:

www.recording.org/users/acoustics

This sidebar, "The Numbers Game," is at the very end, or just click it in the table of contents at the top of the page.

--Ethan