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Noise pollution

How is Aircraft Noise Measured?

We can only measure precisely the sound pressure levels – in other words, how big the vibrations are. The levels of annoyance caused by certain sounds is much more subjective and depends on a range of other factors. Sound pressure levels are are measured in decibels (dB). This is a logarithmic scale which is hard to fully understand, but crucially, an increase of 10dB normally equates to a doubling of loudness. So perfectly simple to measure the decibel level of an individual aircraft as heard from a certain point. (Of course the decibel levels will decrease with distance.)

However, this would not actually reflect the way our ears respond to sound. We are more sensitive to mid- and high frequency sound, though conversely low frequency sound can travel further. (This is why you hear the bass through the walls of a nightclub.) So the measurements are adjusted to try to approximate the response of the human ear. The types of weighting which can be used are A, B, C and D. A-weighting was designed for quiet sounds, D for the loudest. However, it is currently common for A-weighting to be used across a range of transport, industrial, community and recreational noise generating sources, and so the noise levels will be expressed as dBA (decibels A-weighting). This includes aircraft. As aircraft sounds are obviously loud and have significant low frequency components, most campaigners believe this is inappropriate, and either C or D weighting should be used. This is echoed by the The World Health Organisation (WHO) Guidelines for Community Noise:


“Since A-weighting underestimates the sound pressure of noise with low frequency components, a better assessment of health effects would be to use C-weighting”.


Aircraft noise figures for airports are also an average. Measurements of aircraft noise are taken continually over a set period of time, and an average calculated and expressed as Leq – or equivalent level. As it will also be A-weighted, it is called a LAeq – and if measured over a one hour period, it is written Laeq1hour

Again, this does not adequately reflect the impact of aircraft noise, as the average figure includes the quiet periods in between the short loud sound events caused by the aircraft. Again, the WHO Guidelines state:


'where there are distinct events to the noise such as with aircraft or railway noise, measures of the individual events should be obtained (using for example LAmax) in addition to LAeq measurements'

It also does not adequately reflect the impact of increasing numbers of aircraft; the Laeq figure could be almost unchanged if the extra aircraft were only modestly quieter, even though an increase in aircraft noise would be clearly perceptible.

Furthermore, sound level meters have adjustable response time settings – usually 'slow', 'fast' and 'impulse'. Again, although WHO uses the "fast" setting in their Guidelines, BAA/AAD has used the "slow" setting and for aircraft this will result in a lower reading in dBs and understate the actual noise heard. It is believed that the difference can be as much as 10dB between “slow” and “fast” settings.



Community & Health Effects of Aircraft Noise

The most widespread, and obvious, problem of aircraft noise is simply annoyance to the community. The Government claims that "the onset of significant community annoyance" starts when the noise from aircraft averages out at 57 decibels, known as 57dB(A) LAeq. However, the World Health Organisation (WHO) recommends the following noise level limits:

A study entitled 'Attitudes to Noise from Aviation Sources in England' (ANASE), commissioned by the Department of Transport in 2001 and completed last year, also suggests that significant annoyance starts at around 50 decibels. The DfT is currently refusing the publish the study.

In any case, the National Noise Attitude Survey carried out by the Building Research Establishment (BRE) for DEFRA in 2001, revealed that:

This means that 4 million people are moderately or extremely annoyed by aircraft noise, with just over 1.1 million of those being extremely annoyed.

But there are many health effects of aircraft noise which are rather worse than mere 'annoyance', which can always be dismissed as subjective. (There are people in the flight path of Southampton Airport who love the sound and sight of the planes coming over.) A study at Stockholm Airport, reported in “Occupational and Environmental Medicine” magazine in 2001, found that living under a flight path can increase the likelihood of having high blood pressure by 80%. The WHO estimates that in the UK 3,000 people in 2006 as a result of coronary heart disease triggered by long term exposure to noise. In addition, it has linked noise to sleep deprivation and tinnitus. (Tinnitus sufferers hear a constant noise in their ears.)

Aircraft noise also affects the cognitive development of children. A study by FICAN Symposium in San Diego, California, into the FICAN Symposium, February 16, 2000 San Diego, California into the Effects of Aircraft Noise on Children’s Cognition and Long Term Memory concluded that there are impairing effects on long-term recall, both from acute and chronic noise exposure; that the noise effects are not mediated by attention; and that aircraft noise is more impairing than road traffic noise and irrelevant speech (i.e. other children talking out of turn). More recent research between 2001 and 2005 by Stephen Stansfield and Mary Haines at the University of London, Centre Lead for Psychiatry at Queen Mary, University of London, also found that excessive exposure to aircraft noise was linked to lower reading ages and increased levels of annoyance in children.


There is little prospect of significantly quieter planes being introduced over the next 20 years. The International Civil Aviation Organisation (ICAO) set a tougher standard for new aircraft noise that came into force until 1 January 2006. However, the standard is already met by 98% of aircraft currently in production. ICAO also agreed that there should be no global phase-out of existing “Chapter 3” aircraft to speed up the transition to quieter aircraft. This means that the sort of expansion envisaged in the Aviation White Paper will inevitably lead to more people across the country being exposed to higher levels of noise (a fact proven even by the Government’s own noise calculations).

BAA Southampton are doing a public consultation on the noise plan.  You can find by visiting www.southamptonairport.com and click on Noise Action Plan 2009.