Luton and District Association for the Control of Aircraft Noise

Characterising aircraft noise exposure around airports

Noise around airports is most often presented in terms of the equivalent average noise energy, Leq, in dB(A) units for aircraft movements within specified hours of the day and over a specified number of days. The resulting noise indicator is, therefore, averaging the intense noise events which occur as ‘planes fly over and the longer periods of quiet between the events.

The most common such noise indicators are for the 16 hours of between 07:00 and 23:00 (daytime) and 23:00 to 07:00 (night), both for an average operational day based on the 92-day summer period 16 June to 15 September. The official night-time noise index in the UK is the 8-hour Leq between 2300 and 0700. Contours are plotted at 3 dB(A) intervals from 57 to 72 (daytime) and 48 to 72 (night).

However, the European Commission 2002 community noise directives now require new presentations for the purposes of noise mapping and airport noise controls (although there are currently no plans to change the official index for other purposes such as planning of development near airports): Lden (day, evening, night) is a full 24-hour, 365 day indicator in which, to reflect the public’s greater sensitivity to noise at these times, flights in the evening period (19:00 to 23:00) are weighted by having 5 dB(A) added to the noise they are assumed to generate and those at night (23:00 to 07:00) 10 dB(A). Lnight is the same as the 8-hour Leq except that it is produced for the full year, not 92 summer days.