Since 1990 a noise monitoring system (NMS) has been developed around Brussels Airport. It consists of 21 noise monitoring terminals and is managed by The Brussels Airport Company. These noise measurement terminals continually register the aircraft noise as it is heard on the ground.

The noise meters are connected to a central computer that receives and processes the noise data from the various NMTs. The same computer also receives and processes the flight data registered by the Belgocontrol air traffic control centre (CANAC) at the airport. Flight data include information on the type and route of each aircraft.
The link between the individual flight data and the noise data makes it possible to map aircraft that deviate from the normal route ('corridor') or produce an abnormal amount of noise.

What is the function of the noise monitoring system?
The network has several functions, namely:

• A control function. As mentioned above, the link between noise data and flight data makes it possible to check whether individual aircraft do not produce excessive noise or deviate from the normal flight routes. This control also enables us to follow up and support possible complaints made by people living in the neighbourhood. This way of monitoring has induced airlines to adopt a more correct flight behaviour.
• A measurement function. 'To measure is to know'. The systematic noise registration makes it possible to follow up the evolution of aircraft noise closely. This supplies us with extensive information that is used, among other things, to establish the noise contours.
• An analytical function. On the basis of the ever-increasing database with noise data we can carry out a large number of analyses. We can examine, for example, the flight behaviour of individual flights or find out which areas have the most aircraft flying over. Furthermore, we can make simulations to determine the consequences of a possible change in flight routes.

On which basis were the measurement locations selected?
The implantation of the measurement locations was determined on the basis of the normal flight routes.

The NMTs located at a large distance from the airport serve to measure the noise of overflying air traffic. NMTs at closer range not only register the noise of aircraft flying over, but also the noise of aircraft on the ground.