Living near an airport
Since night flights
started to and from Liège-Bierset airport, in March 1998, residents
living under the flight path have been finding it hard to get a good
night's sleep. Anxious to guarantee these people acceptable living
conditions, the Walloon Region was faced with something of a dilemma:
acoustic research offices generally concern themselves with sounds
produced inside a room. As the aim here was to deal with noise created
by aircraft, the MET (Walloon Ministry of Civil Engineering and
Transport) in the end decided to adopt a new approach based on inside
and outside conditions. What does this mean exactly?
In order to guarantee sound proofing for the outside part of home the General Directorate for Technical Services (DGST) agreed on 1 January 1999, to create the EDSI (Design Studies, Estimates and Monitoring Unit for Soundproofing Works) unit. Its five technical teams, backed up with an administrative and counselling section (able to explain to residents the approach adopted), started the ball rolling by setting up various test sites in areas around the two Walloon airports. In so doing, the unit was able to develop effective methods, training resources and a business qualification system (Qualisound). In the wake of the Walloon Government's 31 May 2001 decree, the EDSI unit has been involved in carrying out sound surveys prior to home sound proofing activities, providing an administrative follow-up to the process, and checking the work has been effectively carried out.
Acceptable levels of comfort in dwellings located close to airports
first of all involve measuring the acoustic performances of buildings
located in the various zones. This stage enables the engineers to build
up a picture of the zones and buildings so as to establish the level of
external noise, collect statistics and develop specific projects.
The acoustic performance of a building is obtained by creating a standardised external noise of 120 decibels. This is produced by a source fixed on a 9 metres high mast reaching to the rooftop. The engineers measure the level not only outside but also against a building and in all the rooms of a house. The difference between the results recorded inside and outside the room provides the dwelling's sound insulation.
The survey also takes account of reverberations inside the room, as
this affects the inhabitants perception of noise (the crack of a
revolver is used in this case). Each house is "sketched", photographed
and described in great detail: the size of the rooms and doors, the
material used, the whereabouts of sound leaks, the thickness of the
glass panes and walls.
Back at the office, the engineers use a sound level metre to obtain the sound attenuation for each room. Sound proofing of between 25 and 35 decibels is generally recorded. This means that if an aircraft produces a noise measuring 90 decibels, someone inside a house will hear a noise measuring between 65 and 55 decibels. That is quite a lot: the figure should ideally be 55 decibels in living rooms and 45 decibels in bedrooms. These thresholds have been adopted by a working group chaired by the DGST's (General Directorate for Technical Services) Director-General and comprising three acoustical engineers, two doctors and several representatives of the administration.
Improving the outer cover
The members of the EDSI unit initially created a "sound register" for zone B dwellings (a total of 1,709 homes). The aim of the test sites was to achieve the best possible architectural solutions and produce the required sound levels. The EDSI unit took the opportunity created by these sites to develop innovative technologies and establish standard specifications. Work carried out in the occupied dwellings generally involves improving the outer cover (frames, doors, roofs), intermediary floors (false ceilings) and room ventilation. The operations also focused on sound proofing eaves and attics (placing rock wool on the floor, between the beams and rafters, then lining with plaster boards). Ventilation systems are also installed: an air extractor with acoustic piping (in a bedroom, for example), a dual-flow ventilator in the eaves, etc.
Qualification of businesses
Individuals are increasingly calling on the services of building specialists to help them provide an effective solution for minimising unwanted noise. In order to guarantee the availability of top-quality services, the EDSI has developed a company rating system that is now recognised on a federal basis: Qualisound.
The EDSI is seeking to create specially adapted sound proofing specifications. Cooperation offered by business operators, experts and technical instructors has resulted in a frame of reference being drawn up: the MET manual. n° 4.
Walloon sound insulation policy is in keeping with an EU Directive based on the "European Commission's "Green Paper on future noise policy". The Commission report urges motorway or airport operators to protect people living nearby from unwanted noise.
Noise exposure plan
Providing a means of identifying homes suffering from noise pollution in areas around airports (or motorways), the noise exposure plan is based on the LDN: the noise Level during the Day and Night. Over a 24-hour period the plan records the number of planes, their flyover time and their maximum noise level (a "penalty" equal to 10 dB is added for planes flying at night, that is, between 10 o'clock at night and seven o'clock in the morning). The various zones are defined as follows:
A future Walloon noise pollution management office, the EDSI is available during office hours to deal questions from private individuals and business operators about acoustics, sound proofing aid procedures and so on.