Planning

How Is Aircraft Noise Generated?

How is aircraft noise generated?
Aircraft noise is produced by the aircraft engines and the airflow around the aircraft body and wings. The engines are responsible for much of the aircraft noise during takeoff and climb, while the airflow is typically causing noise during landing as the aircraft has deployed its flaps and landing gear.

How much noise does an aircraft make?
Different aircraft types with different engines, speeds, and shapes produce different noise levels. Furthermore, different weather conditions such as air pressure, temperature and wind also affect noise levels. Today’s modern aircraft produce 75% less noise than those built 40 years ago and new aircraft will continue to present new technology that will further reduce noise footprints.

The charts below provide an indication of the altitude for both arriving and departing aircraft.

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N-Contour system
A useful measure to describe aircraft noise levels is the N-Contour system, developed by the Australian Government in consultation with the aviation sector. 

The N contour system measures the number of aircraft noise events per day exceeding 70, 65 or 60 decibels. For example: 

  • N60 = 100 or more events exceeding 60 decibels per day.
  • N65 = 50 or more events exceeding 65 decibels per day.
  • N70 = 20 or more events exceeding 70 decibels per day.
  • Night contours = 6 or more events exceeding 60 decibels per day.

To find the N-Contour for your area, enter your address using the Melbourne Airport Noise Tool, and click on the N- Contour tab (right hand side).  N-Contours are designed to illistrate indicative noise levels and numbers of aircraft in the areas surrounding an airport.

The diagram below provides a comparision of different types of noise and their common decible ratings.  There are considerable differences in how different people respond to the same noise levels. It also depends on the duration and frequency of the noise events and the time they take place.

It is important to note that a sound becomes twice as loud for every 10 decibel increase.

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