Floor/ceiling assemblies are generally written in terms of Impact Insulation Class (IIC), ASTM E 492, which measures impact sound transmission through floor/ceiling assemblies via a tapping machine. Armstrong believes that the relative merits of floor/ceiling systems are not always properly reflected by IIC ratings. Resilient flooring products will not subdue reverberant noises originating from such sources as typewriters, telephones and conversation. Resilient floors, as with other flooring materials, will have little effect on airborne sound transmission between contiguous rooms. Therefore, flooring materials do not significantly reduce the Sound Transmission Class (STC), which is a rating of airborne sound transmission loss of the floor/ceiling assembly or the partitions.