To measure impact sound, a standardized machine taps on the floor repetitively with metal hammers. A receiving device is placed in the room below to measure the sound in decibels and across a range of frequencies. The resulting score is the Impact Insulation Class rating, or IIC.
IIC ratings can range from as low as 25 up to 110. The higher the score, the more impact sound is reduced. The International Building Code requires a minimum IIC of 50, however, most people can still hear sounds through a barrier until we reach a score of 65.