Air traffic noise register

Noise nuisance related to air traffic has been modelled every year since 2006: the map of the noise register pertaining to air traffic shows the contours of the annual noise levels that exceed 45 dB(A). In 2014, three quarters of the Brussels territory suffered from the noise impact of air traffic. This impact is higher than the impact observed over the last five years, whereas the traffic itself has remained at the same level of magnitude. This is due to the implementation of a new dispersal plan which has resulted in flights passing over neighbourhoods which were not previously flown over. The largest noise levels were observed around the airport and below the air routes of the Canal, the north ring, and towards the east. In 2014, slightly more than one tenth of the territory (13%) was affected by noise levels (Lden) which exceeded the limit of 55 dB(A).

Air traffic is affected by the consequences of the economic and financial crisis

Brussels Airport is Belgium's first airport: in 2014 it recorded around 232,000 flight movements (Source: Brussels Airport).

Globally speaking, the number of movements at the airport on an annual basis (landing and takeoff) has dropped since 2001 (around 325,000 movements in 2000 compared to around 250,000 movements in 2002). This is the result of the events that occurred on 11 September 2001 and the bankruptcy of Sabena. The economic and financial crisis of 2009 added to this, with a special event in 2010 when the ash cloud reached Europe after the eruption of the Icelandic volcano in April.

The proximity of this large airport causes noise nuisance when airplanes fly over the Brussels Capital Region. About half of all movements may have an impact in the Region.

2014: a year marked by a new dispersal plan

In 2014, a new dispersal plan was implemented for flights taking off from Brussels Airport. Following the implementation of this plan, numerous neighbourhoods, including some densely populated areas, were flown over by aircraft whereas this was not the case previously, or to a lesser degree.

Assessment of noise from air traffic

To assess the nuisance in the living environment of the inhabitants of Brussels, an 'acoustic' site description of the territory has been made each year since 2006. The most recent one dates from 2014.

The purpose of this site description is to quantify the 'structural' noise from air traffic and to create a model of the annoyance experienced by the population. The resulting maps of this modelling are called the 'air traffic noise register'.

This register determines the L_den (the day-evening-night level), which represents the weighted equivalent noise level over 24 hours that was observed, on average, for an entire year. For the weighting a penalty factor of 5 dB(A) is applied during the evening (7 p.m. to 11 p.m.) and of 10 dB(A) during the night (11 p.m. to 7 a.m.), as noise at those times is experienced as a greater annoyance. However, L_den is not directly representative of the 'noise peaks' that occur when planes fly over; for this, other, so-called 'event indicators' are used.

The register also determines the L_n (the night level), which corresponds to the equivalent noise level between 11 p.m. and 7 a.m.

Increased exposure of the territory to the noise related to air traffic in 2014

Air traffic noise register of the Brussels-Capital Region in 2014 – Indicator L_den

Sources: Brussels Environment, 2015, 'Cartographie du bruit du trafic aérien en Région de Bruxelles-Capitale – année 2014', based on traffic data for 2014, the ECAC-1997 method and modelling software CadnaA

Note: Only the air routes used are shown on the map.

Three quarters of the Brussels territory suffered from the noise impact of air traffic in 2014. This level is significantly higher, in comparison with the previous 5 years (for example it was two thirds in 2011: see the previous State of the Environment). At issue: the implementation of a new dispersal plan. Put another way, more neighbourhoods were flown over in 2014. The surface area not exposed to the noise from aircraft (L_den < 45 dB(A)) – in the south-east of the Region in particular - has inevitably been reduced. This greater impact is reflected in particular by an extension of the regional surface area in which the noise levels are between 50 and 55 dB(A) (30% in 2014 versus 17% in 2011 for example).

During the night, the surface area exposed to noise nuisance related to air traffic is also significantly greater (19% in 2014 versus 15% in 2011).

Two strips going from the north east of the Region are particularly visible for the L_den indicator, and to a lesser degree for L_n: one is situated along the route of the Canal and the other follows the left-hand curve towards the east. In the case of the L_den, a third strip is noticeable above the eastern ring of the capital owing to landings on runway 01. All of these show the dominant contribution of certain air routes.

The influence of these routes varies depending on the period in question: during the week (working days), the route towards the east is used more than on the weekend, whereas the Canal route is used more on the weekend than during the week. This observation holds true for both indicators (L_den and L_n).

Exposure of the territory to extreme noise levels

The highest noise levels (L_den > 55 dB(A)) concern slightly more than one tenth of the territory (13%). They mostly affect the north east of the Region (north of the city of Brussels - particularly Haren and Neder-Over-Heembeek, Evere, north and east of Schaerbeek, north west of Woluwe-Saint-Lambert) as well as a tiny area to the north east of Woluwe-Saint-Pierre. These are influenced by the air routes from the north ring, the Canal, and those heading east.

During the night, annoying noise levels (L_n > 45 dB(A) affect an area which covers the areas previously mentioned, although it is slightly bigger (19%) (given that the WHO considers that sleep disturbances are deemed to be between moderate and strong from 40 dB(A) and above). The air routes of the Canal and those heading east leave a bigger mark in the south of the Region: they also affect the north west of the city centre and a border zone between Etterbeek and Woluwe-Saint-Pierre.

Evolution of the surface area exposed to a L_den level ≥ 55 dB(A) or a L_n level ≥ 45 dB(A)

Sources: Brussels Environment, 2015, 'Cartographie du bruit du trafic aérien en Région de Bruxelles-Capitale – année 2014', based on traffic data for 2014, the ECAC-1997 method and modelling software CadnaA

Although the evolution of the L_den and L_n indices for extreme noise levels matched the level for air traffic overall between 2006 and 2013, 2014 was different in that there was a decoupling between the number of movements and the regional area exposed. Compared to the period 2009 to 2013, the area exposed in 2014 grew sharply. This partially holds true for the L_den indicator, but it is especially the case for the L_n indicator.

It should be reiterated however that the main changes observed for the L_den indicator in 2014 concerned noise levels lower than 55 dB(A).

As was the case in 2014, the choice of air routes can have a direct impact on the territory exposed, just like the volume of traffic. Other factors are likely to influence the contours of the noise levels, such as the use of runways or even the fleet used (i.e. types of aircraft).

Air traffic generates less noise nuisance than road traffic

The noise related to air traffic occupies the second place in the ranking of urban noise nuisance due to transport (expressed in number of inhabitants exposed). First on this list is the noise caused by road traffic. Third comes rail traffic. This second place does not mean that isolated events cannot disturb a lot certain persons.

We also wish to emphasise that these conclusions are based on a model on the scale of the Region and are representative of the situation over a whole year.