The distance between you and an airplane flying over your head plays a role in how you perceive aircraft noise, and our noise abatement procedures are designed to keep the airplanes as high as possible, for as long as possible, without compromising the safety of passengers in the aircrafts or the communities below them.
However, environmental and logistical factors can also influence the noise you hear.
Environmental factors
Atmospheric or environmental conditions have a major impact on aircraft noise. The reverberation of sound waves caused by weather may actually make noises seem louder, or quieter, than they are. This is due to the physics behind how aircraft noise travels to our ears, and why aircraft flying at altitudes that normally produce no noise may seem louder.
Wind
On a gusty day, airplane noise is moved around in the air. More people hear it but it's not as intense because it's being redistributed to a wider area.
Fog
Like wind, fog can absorb or reflect noise. This can either increase or decrease the perceived noise level.
Cloud coverage
Depending on the thickness of a cloud, airplane noise will bounce off the ground back up into the sky and bounce off the cloud right back down. It won’t be as intense the second time around, but it may amplify the original sound, depending on the cloud height.
Time of day
Noise, like heat, is energy, and energy sources are drawn to each other. During the day, when the air is warmer than the ground, noise energy from an airplane staying in the air, so while you can still hear it, it seems quieter. Conversely, at night, when the ground is warmer than the air, the noise is drawn down, making it seem louder.
Topography
Rich greenery absorbs sound, which means less of it gets to your ears. If you were standing in the middle of a forest as a plane flew over your head, it would seem quieter than if you were standing in a parking lot where the sound is reflected to your ears instead of being absorbed.
Direction of sound
And like sunlight, noise will bounce off hard surfaces, essentially amplifying it. This is also the case when a plane flies over water, and the same reason why you can sunburn faster in the water. Like noise, the sun's rays will reflect off the water and get you twice.
Individual perception
How people react to noise and how they perceive it is a complex issue and can vary from person to person – what’s annoying to one person may be acceptable to another.
While an Airbus A320 flying overhead may generate the same decibel level as a vacuum cleaner approximately five metres away, the aircraft may seem more annoying to a person because one expects to hear the vacuum's noise and is therefore willing to accept it. Similarly, quieter noises that occur frequently may be considered as annoying as infrequent, louder noises.
Repetition
There are distinct flight paths in and out of Toronto Pearson that all airplanes follow. This means that people who live under the flight path experience repeated occurrences of airplane noise. You could compare this to a dog barking next door – it’s not ear-shatteringly loud, but the constant repetition can become annoying.
Time of day
People are more sensitive to airplane noise depending on what they’re doing, and that has a lot to do with when the noise is being experienced.
Most of the airplane noise experienced by people on the ground is unavoidable. These noise levels can change from day to day based on the air traffic at the airport or the weather-dictated operation planes are following.