Impact sound transmission testing is undertaken to floors only. This test is different, a calibrated Norsonic ‘tapping machine’ which comprises of five ‘hammers’ driven up and down by a cam and electric motor is used to “tap” the floor surface by applying a known force on the floor structure. The machine is placed in several pre-determined positions. The resulting noise is measured in the dwelling below, using a sound level meter.
Thereafter, background noise measurements are made using a class 1 sound level meter in the receiving room and are used to apply appropriate corrections for external sound such as traffic noise. Similarly the reverberation time (the time taken for sound to decay by 60dB) is measured within the receiving room using the sound source and a sound level meter to determine the corrections that must be applied to account for the characteristics and absorptiveness of the room.
The measured noise levels in the receiving room are corrected for background and reverberation characteristics determine the impact sound insulation performance of the floor. For the impact noise the lower the measured level, the better the performance as less sound is being transmitted into the dwelling below.
The time taken to undertake sound testing varies from project to project as no site is exactly the same. Taking into account the standard site conditions impact testing is usually undertaken as part fo a 6 pack test, consisting of 2 airborne wall, 2 airborne floor and 2 impact sound tests. A standard 6 pack test will usually take between two and three hours, although this is dependent on our engineers having full free uninterrupted access between all the units/rooms under investigation.