At The Gillespie Group, we rate our sound control systems using IIC (Impact Insulation Class) and FIIC (Field Impact Insulation Class) ratings. The IIC ratings are determined by the sound resistant tests in a lab while the FIIC is the material’s sound resistance once fully installed. These ratings measure how much a material reduces the impact noises. Higher IIC and FIIC ratings equate to better sound resistance, so impact noises like jumping, scraping, and footfall are reduced.