In fact, the soundscape is much better today than it was 10, 20 or 30 years ago, for a very simple reason: planes are much quieter than they used to be. The phasing out of Chapter 2 aircraft in 2002 was a major factor in soundscape improvement.
The NEF (Noise Exposure Forecast) contour is calculated using modelling software that takes into account arrival and departure flight paths, flight destinations, as well as takeoff and landing procedures. The calculation also considers aircraft type, hours of operation, and which runway is used.
Since the restrictions issued by Transport Canada for land-use planning apply in consideration of the NEF 30 contour only, ADM is now using NEF 30 to track the evolution of the soundscape at Montréal–Trudeau.
The map below illustrates the gradual shrinking of the NEF 30 contour around Montréal–Trudeau over the years, and this despite the increased traffic and the construction of new homes near the airport. The NEF 30 contour defines the zone within which aircraft noise can cause a certain degree of disturbance.
It is important to note that, in collaboration with the National Research Council of Canada, Transport Canada recently updated the methodology it uses to calculate NEF noise contours in Canada, both from an IT standpoint and with respect to aircraft noise data. Specifically, Transport Canada now uses the same Federal Aviation Administration (FAA) database, which contains up-to-date information on about 350 types of aircraft. The new software factors in the characteristics of more modern airplanes, their improved performance, new noise certification standards, and the greater diversity of airplane models and engine systems. Application of the new methodology has created variances from the former method.
The 2014 NEF 30 contour shows that Montréal-Trudeau’s noise footprint covered an area of 17.4 km² in 2014, down 58.8% from 42.2 km² recorded in the 1995 reference year. The population living within the noise footprint has shrunk by 91.6% since 1995, from 39,421 to 3,304 residents. The improved soundscape stems mainly from the modernization of the air fleet, particularly the phasing out of noisier (Chapter 2) aircraft in 2002, and from ADM’s implementation of noise abatement measures.