Contact Sound

What is contact sound?

A structural element is brought into vibration, for example when drilling, climbing stairs, walking floor etc.

Determination Method: Research – Measurements:

Within homes, mainly apartments, noise pollution can be caused by hard floor-covering. because hard floor-covering is an ever rising popularity, it has become a growing problem. The impact sound insulation can be improved by using a resilient intermediate layer. The thickness (mass density) of the existing floor can sometimes be extremely low. This means that the resilient middle layer has to be very thick. The quality of impact sound insulation is measured according to NEN 5077. For the measurement of impact sound, a sound generator is used. In technical jargon this is called a hammer device. The hammer device is equipped with 5 steel hammers which successively release a rhythm of 10 beats per second from a height of 4 cm above the surface. The hammer device is calibrated by accurately determining the drop height of the hammers with the aid of a supplied spacer.
Furthermore, In the reception area the reverberation time is measured to compensate for the size and upholstery of the reception area; as they also affect the sound that the impact sound generator produces in the reception area.

Buildings Decree 2012

The noise level for impact sound is Lco (Buildings Decree 2003); L_nT,A (Buildings Decree 2012).

L_nT,A

From the aforementioned measurement, any number can be calculated in order to assess the impact sound insulation. The index for impact sound for separated residential structures, the L_nT,A, is at  most 54 dB. A lower L_nT,A means better acoustic comfort. The requirement of 54 dB is included in the Buildings Decree 2012.
The L_nT,A gives an indication of the noise level in a room. When the L_nT,A decreases, the acoustic comfort will increase. Rule of thumb is: L_nT,A must be defined as audible noise level. The lower the value, the less the sound is audible. Here the argument goes that when the L_nT,A approaches the 0 dB, hardly anything can be heard anymore.

Regulation and control measurement

In many contracts that apply to residents of apartments, requirements are registered about floor finishing in order to prevent noise pollution.