Noise around the airport

Why and how is the noise around airports measured?
The noise from planes is measured for many reasons. It is important to know whether the noise levels are going up over time, and if so, by how much.

In Britain, this noise is measured by averaging out the noise levels during the day (a 16-hour day) during the summer period. The amount of noise is given in decibels (dB). This averaging-out means that the day’s high and low levels of noise are levelled out to give a single figure. The Government calls this averaged decibel measurement ‘LAeq’, and this is the most common international measure of aircraft noise. As a measurement, it means ‘equivalent continuous noise level’.

There are other units of measurement that can be used, and you can read about these and other technical noise information in BAAs Issue Brief on noise

What’s the average noise level near you?
In the UK, Government research indicates that people start being annoyed by aircraft noise at 57 decibels, averaged over 16 hours (57dB LAeq). They use this as the starting point in policies on noise from planes around airports.

To show where the different average noise levels are around the airport, the Government has developed maps showing ‘noise contours’. Below is the ‘noise contour map’ for the area around Gatwick. The maps work like a normal contour map that you would use for walking, or in geography. The contours are an irregular shape because you get more noise at the ends of the runway (where planes take off and land) than at the sides.

 Click here to view an example.

The map above shows the contours for the averaged-out 57 decibels (57dB LAeq) for 2003, combining  noise for all flights, regardless of the wind direction and therefore of the direction the planes were flying.

How many people are affected?
In the last 20 years the 57 decibel noise contour has shrunk. This is because planes are quieter than they used to be. As a result the number of people who live within this noise contour has reduced to reflect this.

In 1993, there were14,600 people in the 57 decibel noise contour around Gatwick. By 2003, this had fallen to just 4,100 people.

This is despite a rapid growth in air travel at the same time, from around 191,000 flights a year in 1993 to 242,700 flights in 2003.