IIC, or Impact Insulation Class, is an acoustical rating that measures the sound insulation and transmission of impact noise, such as vibrations or footsteps, on a floor-ceiling assembly. The IIC rating of a floor product is expressed using whole numbers and is based on the entire assembly on which it sits on, including the floor covering itself and any applicable underlayment, subfloor, and ceiling system. Soft floor coverings or ones with cushioned backings, underlayment, or resilient material components can increase the IIC rating, with higher ratings contributing to lower impact sound transmission and better acoustic insulation. The International Building Code (IBC) requires an IIC Rating of 50 for all floor-ceiling assemblies separating dwelling units. This can be determined using standardized test procedures such as ASTM E492 Standard Test Method of Impact Sound Transmission Through Floor-Ceiling Assemblies Using the Tapping Machine and ASTM E1007 Standard Test Method for Field Measurement of Tapping Machine Impact Sound Transmission Through Floor-Ceiling Assemblies and Associated Support Structures.