IMPACT SOUND TRANSMISSION The method is designed to measure the impact sound transmission performance of a floor-ceiling assembly in a controlled laboratory environment. IIC Flooring 70 5mm Vinyl Plank Sub-floor over a 6” concrete subfloor with a suspended ceiling assembly 55 5mm WPC over a 6” concrete slab SOUND TRANSMISSION LOSS The sound-insulating property of a partition element is expressed in terms of the sound transmission loss.