The standard tapping machine is the most commonly used source for impact insulation testing of floors and floor coverings. In this paper the stages of the transmission of impact noise through a floor are considered. The force spectrum of the hammer impulse is calculated digitally. By assuming that the cushioning effect of the floor covering can be separated from the concrete floor on which it is laid, it is possible to predict the sound field produced by the tapping machine. It is necessary to know the sound field produced by the tapping machine on the bare floor and the force spectra of the hammer on the bare and the covered floor. The predicted results agree well with measured cases. This validates the definition of the behaviour of a floor covering in terms of impact insulation improvement when used on concrete slab floors. It also shows that impact insulation improvement can be calculated from a knowledge only of the hammer impact spectrum. An ageing or hardening process which occurs after successive hammer blows on soft floor coverings is also described.