To measure the impact sound insulation of the structures a standardized sound source, the tapping machine, must be used. There is five steel hammers in the machine, each of them weighing 0,5 kg. Every hammer falls 40 mm before hitting the floor twice a second. The airborne sound is neglected in the tapping room, only the sound pressure level, produced by the structure-borne noise, is measured in the receiving room. The measurement is made at 16 bands at the frequency range from 100 to 3150 Hz.
The results measured in the receiving room are expressed as a graph of sound pressure levels made by the tapping machine. Then a comparison with the reference graph will be made and the weighted normalized impact sound pressure level L'n,w is the value of the reference graph at the centre frequency of 500 Hz.
