This page explains the basics about Luton Airport for people living in the area affected by it noise, so you understand the issues.
Who’s who?
Luton Airport is owned by Luton Borough Council (LBC), which makes money from it and is also its Local Planning Authority.
Ownership is via a wholly-owned subsidiary company called ‘London Luton Airport Ltd’ (LLAL), which brands itself Luton Rising. Its board includes elected Members of LBC.
Luton Rising does not have the expertise to run an airport, so under the Airports Act has to appoint an independent qualified airport operator – in Luton’s case that is Spanish-owned ‘London Luton Airport Operations Ltd’ (LLAOL).
The parties above often refer the the Airport as London Luton Airport, or LLA.
How are community issues raised with the Airport?
There is a statutory consultation group called the ‘London Luton Airport Consultative Committee’, or LLACC, in which LBC, LLAL and LLAOL staff meet representatives of other local councils and local community groups.
LADACAN – the Luton And District Association for the Control of Aircraft Noise – is a community group which sits on the LLACC to represent members’ views and fight for better recognition of the community perspective.
How is aircraft noise measured?
There’s a confusing mixture of ways to measure and describe noise. For aircraft noise, it can all be boiled down fairly simply.
Loudness is measured on a scales of decibels (dB) which ranges from say 40dB (normal countryside background) to 90dB (noisy plane taking off). By general agreement, an increase of 10dB in peak loudness sounds twice as loud to our ears, and most people can detect a minimum loudness change of 3dB – some are more sensitive.
A loudness measure is called Lmax, so a very noisy flight would be 80-90dB Lmax, a noisy one around 70dB, a middling one 60dB, a quieter one 50dB. Obviously the noise you hear depends on how far away the aircraft is – so a given type of aircraft going over you at 3,000ft altitude would be louder than if at 6,000ft, all else being equal.
Aircraft noise is not continuous, since there are different intervals between flights, and the noise of each one rises to a peak and then falls.
Planning conditions often use a single “averaged” number to represent total aircraft noise in a given period (16 hours of day or 8 hours of night) which is, confusingly, also expressed in dB but called Leq16h or Leq8h depending on time.
The averaged values might be say 60dB Leq16h in a noisy area close to an airport where individual flights might have loudness of 80-90dB Lmax, but the average depends not just on the individual loudness but the number in the period.
Increasing the Leq value by 3dB would correspond to doubling the noise from each flight or doubling the number of flights, but it’s not the same as the loudness of each flight or indeed any individual noise – it’s an average.
Noise limits and planning conditions
The Civil Aviation Authority (CAA), the government’s aviation regulator, has defined standard positions for measuring peak noise, 6.5km from where an aircraft starts its takeoff run.
Noise Violation Limits (NVLs) set by airports or planning authorities relate to peak noise at those specific monitoring locations.
Departing aircraft may pass over communities before reaching the noise monitoring location; arriving aircraft may pass over communities after the monitoring location – in both cases making more noise that the specified limit. This is permitted: the limit only applies at that monitoring location.
A set of other noise control planning conditions is often needed, such as:
- numbers of flights within defined periods (eg at night or in the day)
- the maximum Leq noise footprint area for a given dB in defined periods
- the product of the aircraft noise classification and the number flown (often called a quota count)
Misleading information
The aviation industry often uses terms in a misleading way – claiming for example that a new engine is half as loud when although it emits half the noise energy, it only sounds 3dB quieter. As indicated above, it would have to be 10dB quieter to sound half as loud.
The industry also misleadingly classifies a 1dB change in Leq as ‘imperceptible’, when of course it would be very perceptible because it’s a change to an average: if there are 400 flights a day, a 1dB Leq increase would correspond to an additional 60-70 flights.
Noise contours
The noise averages, or Leq values, can be calculated for different places. They tend to reduce further way from an airport as the planes spread out and climb, and increase as you get closer to the runway.
Based on the calculations, the noisiness can be viewed as a kind of hill: the closer to the airport the higher you climb, and like any other hill, contours can be plotted.
A contour joining all the places close to a runway with the same average noise (eg 60dB Leq) will enclose an area, and the size of that area indicates how widely spread the noise is.
Noise insulation
Airports sometimes offer noise insulation to homes located within a given noise contour – an example from Luton’s insulation scheme is shown here:
If your home is in the red contour area they offer you insulation, if not they don’t.
These contours are all computer-generated based on noise models which the airports tend to keep secret – not much use if you want to check them!
When applying for planning permission to change the noise, they re-run the models and the computers then spit out numbers on how many additional homes and offices would fall in a given contour – all very impersonal.
N-numbers
Other contours can be computer-generated to indicate how many flights sounding noisier than a given level will pass over a given location per day.
These are called N-numbers – for example N65 is the number of flights louder than 65dB Lmax (peak noise) at that location in the specified time.
And again, they join these up to create contours linking areas experiencing similar impact.
Aircraft noise affects real people
Different people react to aircraft noise in different ways, depending on:
- how loud an individual flight is
- how long the flight takes to pass
- what time of day or night they occur
- what the background noise levels are like
- how low and visually intrusive the flight is
- whether the overall noise experience has changed
- whether the noise events are all bunched up or spread out
- how often flights affect them at home, at work, in the garden or park
It is completely insulting to represent this as just one number, but industry and government tend to adopt the Leq average because it correlates fairly well to overall annoyance – though the research is very out of date now.
On the next page we show the Flight Tracks around Luton Airport.
For those wanting more detailed information about noise measurement and ways it can be portrayed, we suggest the ICCAN Review of aviation noise metrics and measurement recently produced by the Independent Commission on Civil Aviation Noise – it will certainly help you get to sleep!