FAQ

Soundscape Management Video

1. What is noise, exactly?

Noise is a phenomenon that is omnipresent in the modern world. It is defined as sounds that are undesirable or disturbing. Generally speaking, the louder a sound, the more disturbing it is. Sensitivity to noise, however, can vary greatly from one person to another and even from one moment to another: two sounds of the same intensity may be perceived in very different ways. Some people enjoy listening to a very loud rock concert even though the sound level can sometimes exceed the hearing-damage threshold. But somebody who doesn’t like rock music or is engaged in an activity demanding concentration will be disturbed if they are near the same concert. 

2. How is noise perceived and measured?

Sound is vibration or waves transmitted through the air that can be perceived by ears. Sound is actually minuscule variations in air pressure, which are picked up by the tympanic membrane (eardrum).

Sound has frequency and intensity.

• The frequency or pitch of a sound is measured in Hertz (vibrations per second). The higher the frequency, the higher-pitched the sound; the lower the frequency, the lower-pitched the sound.
• The intensity or level of sound corresponds to acoustic pressure, which is most commonly measured in decibels (dB). Because the human ear’s interpretation of sound intensity varies with the frequency of a sound, sound-level meters use a so-called A-weighting filter, which gives more emphasis to higher-frequency sounds than lower-frequency ones. So ambient noise is measured in A-weighted decibels, or dB(A).

It is important to remember that the decibel scale is a logarithmic scale: 0 dB corresponds to the limit of audibility and 140 dB, to the pain threshold.

Decibels are not additive. Two lawnmowers each generating 60 decibels don’t make a noise of 120 dB, but of 63 dB; similarly, 10 mowers at 60 dB each will generate a total sound level of 70 dB.

An increase of 3 dB (a multiplication of the noise source by 2) is perceptible by our ears. A 10-dB increase in sound level (multiplication of the noise source by 10) is perceived by our ears as double the noise.

3. How do airplanes generate noise?

There are two main sources of airplane noise: engine noise and aerodynamic noise (caused by the flow of air around an aircraft in flight). When a plane takes off, and is using maximum thrust, engine noise is predominant. When a plane lands, the aerodynamic noise that is produced can be as loud as the engine noise.

4. Are there differences from one type of aircraft to another?

Generally speaking, bigger planes make more noise than smaller ones. But size isn’t everything! Engine technology has improved greatly in recent years, so some older, smaller aircraft can be noisier than the latest-generation wide-body jets.

The acoustic performances of each type of air transport aircraft are characterized by three noise-level measurements determined according to procedures defined by the International Civil Aviation Organization (ICAO). These three noise levels are measured on approach, takeoff under full power, and overflight. The standards also consider the mass of the aircraft and the number of engines.

The aerospace industry currently distinguishes between several generations of aircraft, referred to as chapters. 

• Chapter 2: These are older planes dating from before 1977, equipped with earlier-generation engines. Apart from exceptions, these aircraft have not been allowed to fly in Canada since 2002.
• Chapter 3: Aircraft certified between 1977 and 2005. Note that some Chapter 2 aircraft have been fitted with noise-attenuation devices, called “hush kits,” to improve their acoustic certification to meet Chapter 3 requirements. These aircraft are marginally compliant with this standard, so they are louder than aircraft that are certified Chapter 3 when manufactured.
• Chapter 4:  All new aircraft certified between 2006 and 2017 for aircraft over 55,000 kg and to the end of 2020 for aircraft less than 55,000 kg. 
• Chapter 14: Aircraft certified since 2018 for planes over 55,000 kg and since 2021 for planes less than 55,000 kg.

The acoustic performance of new generation aircraft, such as the Airbus A220 and A321neo, as well as the Boeing B737 Max, is considerable compared to older generation aircraft.

Noise Certification - Major Aircraft Operating at Montréal-Trudeau:

Air carriers choose their fleet of aircraft. Airplanes and helicopters must meet international noise certification standards that are adopted by the ICAO Council (International Civil Aviation Organization). These standards take into account the mass of the aircraft and the number of engines. They also establish the method to be used to evaluate noise levels.

Transport Canada issues certifications for the operation of aircraft in Canada. All aircraft must comply with ICAO noise standards that are incorporated in Canadian Aviation Regulations.

When certifying an aircraft, measurements must be made at three certification points corresponding to the approach, take-off and flyover, as shown below (taken from the Aircraft Noise  section of the ICAO site).

Location of certification points for take-off and landing:

• Fly-over (take-off): point located at 6.5 km from the start of rolling (brake-release point), under the take-off flight path

• Approach: point located at 2 km from the runway threshold, under the approach flight path

The levels thus measured are corrected according to the tone of the recorded sounds and their duration. The sound level thus obtained is expressed in EPNdB or effective perceived noise level.  As a result, certification levels can not be compared with those read by sound level meters, which are usually expressed in dB (A).

Certification noise levels in EBNdB (cannot be compared with dB(A) noise levels)

The aircraft below operated 78% of air movements at YUL Montréal-Trudeau in 2022.

Noise certification levels are an average of information from international databases and may differ from the noise certification level specific to each aircraft. The date of certification, the type of engines and the weight of the aircraft can influence the certification of the aircraft.

5. What types of aircraft operate at Montréal-Trudeau?

Virtually all passenger transport aircraft operating out of Montréal–Trudeau are certified Chapter 3 or Chapter 4. There are still some aircraft there were recertified as Chapter 3 because they are equipped with noise mufflers known as "hush kits". These aircraft represent a very small percentage of the fleet operating in Montréal-Trudeau and are used for service to northern destinations. They provide an essential service to these isolated areas.

6. How many runways are found in Montréal-Trudeau and how are they designated?

There is a universal system for naming airport runways. The number of the runway corresponds to its angle vis-à-vis magnetic north. For example, Runways 24L and 24R are at a 240-degree angle, and Runways 06R and 06L at 060 degrees, with the difference between the two directions on the same runway always being 180 degrees. Additionally, when two runways are parallel, they are differentiated by the letters R and L, depending on whether they are to the right or left of one another. Montréal–Trudeau has four runways for navigation purposes: 06R and 24L as well as 06L and 24R.

Runway 10-28, that was the runway intersecting the two parallel runways, was officially decommissioned on November 30, 2023. Its configuration generated several safety and capacity issues. In order to maintain installations to reliability and safety standards and to ensure the fluidity of operations, its vocation has been permanently modified to make it a taxiway. See the Soundscape Newsletter for more details.

 

7. What determines the use of runways in Montréal-Trudeau?

Runway use is dictated first and foremost by flight safety considerations, and particularly by weather conditions. Planes have to land and take off facing the wind. Operational considerations such as aircraft type and runway length are also important. The temporary closing of a runway, for example for repair work, can also have the effect of concentrating traffic on the other runways. Finally, there is a priority runway system in place for night operations.

The table below shows runway use statistics for 2022. Runway use statistics for 2006 to 2021 are available in the Indicators section. 

Runway use statistics - 2022

Runway	NO. OF ARRIVALS	%	no. of departures	%
06L (north)	11,460	13%	1,827	2%
06R (south)	13,746	16%	24,107	27%
10	0	0%	0	0%
24L (south)	30,317	34%	56,542	64%
24R (north)	32,785	37%	6,325	7%
28	0	0%	0	0%
Total	88,308	100%	88,801	100%

 

 

8. Why are there planes over my neighbourhood?

Planes are likely to fly over most of Montréal’s neighbourhoods at any time during the day. The majority of aircraft flying over Montréal take off from or land at Montréal–Trudeau. There are other airports nearby, however, including the one in St. Hubert. Often, planes flying over Lachine, for example, are departing from or arriving at St. Hubert.

After takeoff, jets may bank left or right, depending on their destination, as soon as they reach an altitude of 3,000 feet on the runway heading; and propeller planes must turn as soon as possible after takeoff to clear the way for jets that fly faster. Aircraft landing at Montréal–Trudeau must follow a very precise trajectory, directly in line with the runway and on a 3° angle of descent. Since there are four runways in operation (two physical runways that can each be used in two directions), there are four approach corridors, which take aircraft over many neighbourhoods.

 

9. Why are there more planes at certain times of day?

An airport has morning and evening “rush hours." Air transport is not very different from other modes of transportation. On highways, bridges, as well as subway and commuter trains, there is always more traffic when people are travelling to or from work.

The same goes for air transport: many domestic and transborder flights leave early in the morning, carrying businesspeople who return in the evening of the same day.

On transatlantic routes, planes usually arrive in the afternoon and leave in the evening. To enable two daily turnarounds, some planes serving southern destinations leave very early in the morning, return in the afternoon, take off again, and return late at night.

10. Why do I hear planes on some days but not on others?

It all depends on the wind direction and runway use.

For safety reasons, airplanes always take off and land into the wind. In Montréal, the prevailing winds are southwesterly, so planes most often take off towards Lac St-Louis, mainly from the south runway (24L), and land on the north (24R) and south (24L) runways.

 

 

If the winds are from the northeast, planes take off and land in the opposite direction, on the south (06R) and north (06L) runways.

 

Various factors, such as work on a runway or taxiway, can lead to changes in the normal operating mode.

11. Why do airplanes make more noise in summer?

First of all, people are outside more often in summer and leave their windows open, so they are much more exposed to aircraft noise.

Second, because the air is hotter and less dense in summer, it provides less lift, so planes climb more slowly on takeoff and fly at lower altitudes over areas near the airport.

Atmospheric conditions like humidity, wind and cloud ceiling height can also affect noise propagation and our perception of noise.

12. How is noise measured near the airport?

To measure noise levels, ADM has seven noise monitoring stations installed in the residential areas bordering the airport, plus one mobile noise monitoring station that it deploys as needed. ADM publishes in the Annual Soundscape Report the annual LEQ noise levels (total equivalent noise level) recorded at the various noise measuring stations around the airport. The LEQ indicator reflects the average noise level during a given time period, expressed in dB(A). Since it's use is not specific to aircraft noise, it can also be compared to noise from other sources such as trains, highways, etc.

WebTrak displays in real time the noise levels at the noise monitoring stations. The noise monitoring station's locations around YUL are identified on WebTrak's map by the blue circles.

13. Air traffic passengers are continually increasing. Doesn’t this mean more aircraft movements (takeoffs and landings)?

In recent years, despite a significant increase in the number of passengers, the number of movements has remained relatively stable. However, this number has dropped drastically since March 2020 due to the international health crisis associated with COVID-19.

The graph below shows the trend in aircraft movements and passenger traffic at Montréal-Trudeau from 2002 to 2022.

14. Why was Montréal–Trudeau airport built in the middle of the city?

Montréal–Trudeau airport was built in 1940 on the site of a former horse racetrack. At the time, it was surrounded by farmland. The three maps below, from 1940, 1960 and 1990, show how the city gradually grew around the airport. Urban development continues today. There are high-end residential projects under construction or planned near the airport and under runways' flight paths.

15. Isn’t there a night-flight curfew at Montréal–Trudeau?

There is no curfew at Montréal-Trudeau. Like all major airports and other types of transport infrastructures, Montréal-Trudeau airport is open 24 hours a day.

There are restrictions on night flights, specifically for wide-body jets weighing more than 45,000 kg (e.g., Airbus, Boeing):

• Takeoffs: Midnight to 7 a.m.
• Landings: 1 a.m. to 7 a.m.

Aéroports de Montréal (ADM) does have the right and the authority to grant exceptions for medical emergencies, delays beyond the carrier’s control and adverse weather conditions as well as for some regular flights.

A strict internal policy applies in such cases. In particular, there are only a small number of exemptions for regular flights, and they must be supported by sound operational reasons. The exemptions are also contingent upon adherence to the noise abatement measures in force.

Note also that especially noisy aircraft cannot be granted exemptions for night flights; these include the Antonov, B727, B737 100 and 200 series, B747, DC9, DC10, Ilyushin, L101, MD 80 and MD-11.

16. Why not cease night flights at Trudeau altogether?

The airport remains open at all times to accommodate emergencies, air ambulances as well as general aviation (small private aircraft, which generally are not very noisy). In commercial aviation, night flights, including departures before 7 a.m., are vital because they provide the following advantages:

FOR PASSENGERS

• Return trips can be made in a single day, avoiding overnight hotel stays;
• Final destinations with connections to other airports in Canada and the U.S. can be reached in a timely manner – for example, the 6:30 a.m. Air Canada flight to Toronto provides access to several destinations that are not served by direct flights out of Montréal–Trudeau;
• Travellers get the most out of their holidays at sun destinations because flights leave early in the morning and return late at night.

FOR CARRIERS

• Aircraft usage time is maximized, with multiple turnarounds within a 24-hour period;
• Carriers optimize the use of their networks by co-ordinating connection schedules at their other hubs and those of their partners;
• Companies can provide competitive rates and flexible schedules to meet passengers’ needs.

FOR THE MONTRÉAL COMMUNITY

• A competitive airport that provides international-calibre service;
• A wide range of destinations and flight frequencies;
• Enhances the reputation and economic growth of the Greater Montréal Region.

 

Movements of a typical day for Summer 2019 and Winter 2019