Impact Isolation Class
A measure or specification of isolation effectiveness of building structures from impact noises such as slammed doors, dropped objects, footfalls, shuffled furniture, etc. The higher the IIC rating, the better such isolation. Impact noises can be transmitted through walls, floors, and ceilings throughout a building and re-radiated at distant locations. Careful design and special construction materials (floating floors, isolation pads, resilient channels, spring rails, flexible connectors and hangers, for example) can help improve IIC ratings, which may be thought of as the structure-borne equivalent of the airborne noise ratings addressed by Sound Transmission Class (STC).
The test is performed by placing a tapping machine in a source room and measuring the noise levels in a receiving room, which is located on the opposite side of the partition being tested and is the one most directly affected by the noise. Multiple measurements are conducted for each test. When the tapping machine is activated, the machine taps the floor with five small steel hammers at the rate of ten taps per second. Several measurements are then made in the receiving room to determine the average sound level. The noise levels measured in the receiving room are divided into sixteen one-third octave bands ranging from 100Hz to 3150Hz inclusive. The tapping machine is then moved to a different location where another set of noise measurements are taken. This procedure is repeated two more times for a total of four locations and four sets of measurement data.