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Noise register of air traffic
Since 2006 noise nuisance caused by air traffic has been modelled on an annual basis: the map of the noise situation of the regional territory indicates the contours of the annual noise levels that exceed 45 dB(A). Two thirds of the territory is faced with the noise impact from air traffic. The highest noise levels are observed in the surroundings of the airport and, to a lesser extent, above the canal, the northern ring road and the Sonian Forest. In 2011 slightly more than one tenth of the territory (12.1%) was exposed to noise levels above the 55 dB(A) threshold value.
Air traffic is affected by the consequences of the economic and financial crisis
Brussels National Airport is Belgium's first airport and occupies 16th place among European airports: in 2011 it recorded around 234,000 flight movements (Source: BelgoControl).
Globally speaking, the number of movements at the airport on an annual basis (landing and taking off) 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. For about half of all movements there is a possibility that these may have an impact in the Region.
Assessment of air traffic noise
In order to assess the nuisance for the Brussels environment, an 'acoustic' site description of the territory has been made each year since 2006. The most recent one dates from 2011. Hence, it does not take into account the changes to flight routes that have taken place since then.
The purpose of this site description is to quantify the 'structural' noise from air traffic and to create a model of the nuisance experienced by the population. The results of this modelling, reflected in maps, are called the 'noise register of air traffic'.
This register determines the Lden (Level day-evening-night), 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 hours (7:00 p.m. to 11:00 p.m.) and of 10 dB(A) during the night (11:00 p.m. to 7:00 a.m.), as noise at those times is experienced as a greater nuisance. However, Lden 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 Ln (level night), which corresponds to the equivalent noise level between 11 p.m. and 7 a.m.
Severity of noise nuisance from air traffic
Air traffic noise register of the Brussels Capital Region – Indicator Lden
Sources: Bruxelles Environnement - Leefmilieu Brussel, 2013, ' Cartographie du bruit du trafic aérien en Région de Bruxelles-Capitale – année 2011 ', based on traffic data for 2011, the ECAC-1997 method and modelling software CadnaA
Note: only the flight routes used are shown on the map
Two thirds of the territory of Brussels experiences the noise impact from air traffic. A strip that goes from the northeast of the Region and extends in the direction of the centre of Brussels is particularly visible; it shows the dominant contribution of certain flight routes (in casu the 'ring route' and the 'canal route').
The highest noise levels (Lden > 55 dB(A) affect slightly more than one tenth of the territory (12.1%). It concerns mainly the northeastern part of the Region (Haren and Neder-Over-Heembeek situated to the north of the city of Brussels; Evere; the northernmost part of Schaarbeek; the north of St-Lambrechts-Woluwe; the east of St-Pieters-Woluwe). The noise levels that cause nuisance at night (Ln > 45 dB(A), the threshold considered to be moderately to severely sleep-disturbing by the WHO), are found in an area that is largely identical, but slightly more extensive (14.9%).
Evolution of the surface area exposed to a Lden level > 55 dB(A) or a Ln level > 45 dB(A)
Sources: Bruxelles Environnement-Leefmilieu Brussel, 2013, ' Cartographie du bruit du trafic aérien en Région de Bruxelles-Capitale – année 2011 ', based on traffic data for 2011, the ECAC-1997 method and modelling software CadnaA
The evolution of the indices Lden and Ln generally follows the evolution of air traffic. The reduction of the exposed surface area between 2007 and 2010 corresponds to a decrease in the number of flights (arrival and departure) at Brussels Airport, and the slight increase at the beginning of 2011 to a modest recovery of traffic.
Other factors which may influence the contours of the noise levels are – in addition to the traffic volume – the use of the strips and the flight routes (as illustrated on the map above) or the aircraft fleet (i.e. aircraft types).
Air traffic generates less noise nuisance than road traffic
The noise involved in air traffic occupies the second place in the ranking of urban noise nuisance from transport (expressed in terms of the number of residents 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 cause a lot of nuisance for 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.