Classification

The ability of a product to absorb sound determines its sound absorption coefficient. It can be anything between 0.0, which means no absorption, to 1.0, which is total absorption. The result itself is called the alpha value and is abbreviated as "a". If it says "ap," it means "practical alpha," which indicates it is linked to a specific frequency, while "aw" means "weighted alpha," which is independent of frequency. The alpha value, in turn, determines which absorption class a product belongs to. If the product has an aw of 0.9, it absorbs 90% of sound and belongs to class A. If the alpha value is below 0.15, it absorbs too little to be sound classified at all. In between are classes B, C, D, and E.