Sound Absorption Coefficients

[Vic]

I wonder if someone could explain this to me.

My understanding was that a Sound absorption coefficients of "0" meant full reflection and "1" meant full absorption. So what would a Sound Absorption Coefficient of 4 mean?

Regards

Vic

[Sammas]

Its explained here: http://realtraps.com/art_measure.htm

You may notice that absorption coefficients sometimes have a value greater than 1.0. Although it is impossible for any material to absorb more than 100 percent of the sound, measurements can yield a value greater than 1.0. The main reason this occurs is that all material has a finite thickness, and the edges - which are not included in the stated surface area - absorb some of the sound. So for an acoustic panel two by four feet and four inches thick, the real surface area includes the four-inch thick edge around the material. If included in the measurements, this would add four square feet to the stated surface area of eight square feet - a 50 percent increase! (See The Numbers Game below for a more detailed explanation.) Even when the edges are included in the total surface area, values slightly greater than 1.0 are still possible due to diffraction effects at the material's edges and corners. When the edges are rounded, this effect is reduced.

[Vic]

Hi Nath,

Thanks for the info, that helped a lot. However it says that figures slightly greater than 1 are possible however I am looking at a spec sheets that claims up to 17 at high frequencies?

http://www.acousticsfirst.com/acoustica ... baffle.htm

Vic

[peat]

Look like a mistake to me.
They do seem to correlate with what you would expect from such a material however, but they are scaled incorrectly.

Some of their other values seem to be ok but:
http://www.acousticsfirst.com/sonora-wall-panels.htm