IIC ratings are related to structure-borne sound transmission and can be greatly affected by the flooring.
Acoustical underlayments and floor coverings will improve the IIC rating according to their physical material properties. More rigid materials will be less effective than ones that offer some internal damping or soft/fibrous materials. Keep in mind that:
- No single floor underlayment or floor covering carries an absolute IIC rating by itself.
- The product's rating is always dependent on the rest of the floor-ceiling assembly.
When comparing various products, make sure you compare ratings which were the result of comparable test assemblies.
In other words: don't compare Product A tested on a 8" slab with a gypsum board ceiling to Product B tested on a wood truss assembly with no ceiling.