Vibration and Acoustics/Emerging Noise Calculation
Emerging noise of an installation is the main criterion in the french noise regulation. It is basically the difference between the total noise of the area of the installation and the background noise. The French criteria consider the way the installation affects the background noise in housing areas, so the noise levels have to be measured there.
The main formula:
Emerging noise (dBA) = Total noise (dBA) - Background noise (dBA)
Total noise is the easiest measure to do, whereas background noise must be free of the installation noise. In some cases such as nuclear power plants, it could be clearly complicated because those plants can't be turned off only for acoustical measurements.