Airborne sound

What is airborne sound?

With airborne sound, the air is directly set in vibration, as in the case of speech or sound coming from loudspeakers. Even though the air vibration could cause a wall vibration, which is then forwarded to the underlying space, we can still speak of airborne sound. The quality of a partition wall is the major factor regarding airborne sound. The surrounding structure can also participate: Sound can pass a separation wall through vibrations in floors ands walls, and once past it, it re-emerges as sound. This is also known as a flanking transmission.

Determination Method: Research – Measurements

In order to generate a sound field within a certain space, for the benefit of airborne sound insulation or control measurements of the external separating structure, an artificial sound source is utilized. This will usually consist of a noise generator (white or pink noise) which has an amplifier and reproducer(s). The quality of airborne sound insulation is measured according to NEN 5077. On one side of the separation wall, noise is displayed on a high noise level. In addition, the noise level is measured on both sides of the separation wall. On the revenue side, the reverberation time is also measured to compensate for the size andupholstery of the reception area, as they also affect the noise level in the reception room.From the differences in the level of sound between both rooms, one number is calculated (The Ilu,K (Buildings Decree 2003); DnTA,k (Buildings Decree 2012) per frequency area, after correction of reverberation time, from the set of measurement values.

Buildings Decree 2012

D_nTA,k

The index for airborne sound insulation D_nTA,k is a measurement that serves as a protection against the (air) – noise from neighbouring areas. The index is designed in such way that the D_nTA,k  is to produce at least 52 dB in order for the separation wall to be good enough. The D_nTA,k  indicates the difference in noise levels and will in common usage often be referred to as sound insulation. If the D_nTA,k rises, the acoustic comfort will increase. Rule of thumb is: The higher the sound difference, the better the sound insulation. The requirement of 52 dB has been included in the Buildings Decree 2012.

This national legislation contains regulations that require a minimum level of protection against unwanted noise. For the best protection against noise, whether the noise is coming from outside, from the neighbours or because of installations, higher values should be maintained than those pointed out in the Buildings Decree. The Buildings Decree distinguishes between the requirements that apply between homes and for rooms within homes.