How noise is measured
Why and how is the noise around airports measured?
How we measure aircraft noise
It is important to know whether the noise levels are going up or down over time, and if so, by how much. In the UK, Government research into how communities respond to aircraft noise uses a particular measure known as “the equivalent continuous sound level” - or decibels “LAeq”. Following research, the Government announced that it accepted that the onset of statistically significant community annoyance is 54dB LAeq.
What are noise contours?
Noise exposure is depicted in the form of noise contours. The Government uses these noise contours to show areas affected by the air noise around airports. Similar to height contours on a map which show changes in ground levels over an area, the noise contours show areas where the noise level is above a certain LAeq value. The contours don’t show the noise that individual aircraft make, but rather the equivalent continuous sound level in decibels at a particular location due to aircraft noise.
Every year the UK Civil Aviation Authority calculates the noise made between 07.00 and 23.00 over a 92 day period between June and September to provide LAeq daytime noise contours. Night noise contours are also calculated for the period between 23.00 and 07.00.
Noise contours 2018
Gatwick employs a range of measures to reduce aircraft noise. Improved operational procedures - including smoother descents that reduce drag and use less power - the phasing out of the noisiest aircraft and the introduction of new, quieter aircraft reduced the size of Gatwick’s noise footprint (54dBA Leq) by 7% in 2018 - compared to 2017.
Gatwick’s noise footprint shrank from 82.7 Km2 to 77.1 Km2 in 2018 (compared to 2017), with the number of people living within this noise contour also falling to 10,200 from 10,950.
Read the full Noise Exposure Contours for Gatwick Airport 2018 report. (Note: this is a large file 17MB)
Below is the current daytime noise contour map for the area around Gatwick. It shows the comparison between 2018 and 2017. The contours are an irregular shape because aircraft need to take-off and land into wind. As the wind predominately comes from the west, the areas to the east of Gatwick tend to experience more arrivals noise, and the areas to the west more departures noise.