Impact sound originates when one object strikes another such as footsteps,hammering and objects falling down. It travels through a structure with little loss of energy if the structure is continuous and rigid. Transmission of impact sound can be controlled by isolation; the higher the IIC number the better the impact sound insulation.
The NZ Building Code requirements are set out in Clause G6 “Airborne and Impact Sound”. This clause sets out the performance of building elements between occupancies to prevent undue noise transmission to the habitable space of household units.