This topic is one that is becoming of increasing concern to residents of our Parish.
I have tried to present a summary of how aircraft noise is regulated and measured and how flights are monitored to and from Stansted. To make better sense of this I have also included information on ‘who does what’ in relation to the overall policies on aircraft flights, who implements those policies.
Aircraft noise policy is ultimately determined by Government. In 2013 the Government published the Aviation Policy Framework. Most of this document highlights the economic importance of the aviation sector to the UK economy. In 2013 it directly employed 220,000 people and was valued at £18 billion. We have the third largest aviation network in the world after the USA and China. Aircraft noise is identified as the primary concern of communities near airports and the document states that: “Our overall objective on noise is to limit and where possible reduce the number of people in the UK significantly affected by aircraft noise.”
The regulation of air space is the responsibility of the Civil Aviation Authority (CAA)
“We consider and decide on airspace change proposals that are submitted to us, taking into account safety, efficiency and noise impact on local communities.”
CAA do not initiate changes in routes. These are instigated by the aviation community industry e.g. airports, general aviation or NATS.
In addition, the Government sets the policy approach for use of airspace and airspace change proposal decisions taken by the CAA e.g. narrow flight paths v dispersed flights over a wider area.
NATS (National Air Traffic Control Services) provides air traffic navigation services to aircraft flying through UK controlled airspace and at numerous UK and international airports. These include Stansted Airport. They currently deal with over 6,000 flights a day.
Noise is regulated to some extent at all UK airports. This can include noise limits and restrictions on operations. The specific restrictions will differ from airport to airport, reflecting the types of aircraft that operate there, how busy the airport is and what flight paths are.
Although maximum noise limits are set for occupational noise exposure, there is no limit defined for environmental noise, including aviation noise. However, in order to assess the significance of aircraft noise in the UK, it is generally assumed that if the average noise level in an area from 7.00am to 11.00pm is more than 57dBA L eq , it will be "significantly annoying" to the community that live and work there. The EU has established a corresponding policy threshold of 55 dB L den , resulting in two different measures being used to inform policy at present.
This doesn't mean that noise above these levels will not be allowed. But it does mean that noise will be an important factor in planning decisions within that area (for example, about airport expansion), and that there may be support available for noise mitigation (such as double-glazing).
Measuring Sound and Its Effects
A useful introduction is found on the Federal Aviation Agencies website.
“To understand the methods used to measure noise, it is necessary to have some understanding of how sound is measured and how it affects humans. Some basic concepts include (1) sound waves and their measurement in decibels, (2) human ability to hear the entire range of sounds made, and (3) noise as a source of interference in people’s activities.
First, sound radiates in "waves" from its source and decreases in loudness the further the listener is from the source. As sound radiates from its source, it forms a sphere of sound energy. Sound waves exert sound pressure, commonly called a "sound level" or "noise level," that is measured in decibels. The higher the number of decibels, the louder the sound appears to someone hearing it. But because decibel levels are measured logarithmically, an increase of only 10 decibels -- for example, from 50 decibels to 60 decibels -- doubles the loudness that people believe they hear.
Second, while the human ear can hear a broad range of sounds, it cannot hear all sounds. Sounds with very low pitches (low frequencies) and sounds with extremely high pitches (high frequencies) are generally outside the hearing range of humans. Because of this, environmental noise is usually measured in "A-weighted" decibels. The A-weighted decibel unit focuses on those sounds the human ear hears most clearly and deemphasizes those sounds that humans generally do not hear as clearly. Table 2 illustrates the typical sound levels of some common events.
Table 2: Typical Sound Levels of Common Occurrences
Sound level in
Rock band (indoors)
Dishwasher on rinse cycle at 10 feet
Bird calls (outdoors)
SOURCE: Federal Interagency Review of Selected Airport Noise Analysis Issues (Federal Interagency Committee on Noise; August 1992).
Finally, the impact of noise on communities is usually analyzed or described in terms of the extent to which it annoys people. Annoyance refers to the degree to which noise interferes with activities such as sleep, relaxation, speech, television, school, and business operations. While it is difficult to predict how an individual might respond to, or be affected by, various sounds or noises, some studies indicate that it is possible to estimate what proportion of a population group will be "highly annoyed" by various sound levels created by transportation activities. The findings of a 1978 study that related transportation noise exposure to annoyance in communities has become the generally accepted model for assessing the effects of long-term noise exposure on communities. According to this study, when sound exposure levels are measured by a method that assigns additional weight to sounds occurring between 10 p.m. and 7 a.m., and those sound levels exceed 65 decibels, individuals report a noticeable increase in annoyance.”
In the UK, the results from the Aircraft Noise Index Study 1982 and Attitudes to Noise from Aviation Sources in England 2007 have been relied upon to assess the impact of aircraft noise.
The Department for Transport (DfT) commissioned a Survey of Noise Attitudes in 2014 to address emerging evidence that annoyance arising from aircraft noise had been increasing, building on the earlier noise surveys detailed above. This research study obtained new evidence on attitudes to aviation noise around airports in England and how they relate to UK aircraft noise exposure indices. One of the effects of noise that is hardest to assess is stress. It is known that noise can cause a variety of biological reflexes and responses, which are referred to as stress reactions. However, it is unclear to what extent these might lead to clinically recognisable disease following a period of exposure to noise.
There seems to be general consensus that environmental noise can affect subjective sleep quality and mood the next day, and has an acute impact on heart rate. Some studies have found that children who are chronically exposed to noise experience raised levels of stress, increased blood pressure and mental health effects; but overall, scientific literature to date has generally found that the evidence for long-term impacts on stress hormone levels is inconclusive.
The CAA's CAP 1506 describes the approach to the study, sampling strategy, determination of noise exposure, analytics approach and results. Ipsos MORI's technical report, Survey of Noise Attitudes, provides further information on the noise survey questionnaire, the selection and and sampling process, response rates, participant demographics and survey resources. The raw data (Excel file) is available for review, which includes a data dictionary describing each question and guidance on decoding responses.
Finally, an independent peer review of the survey's analysis and final report was commissioned by the DfT and undertaken by Dr Hannah Devine-Wright (Placewise Ltd) and Stephen Turner (Stephen Turner Acoustics Ltd).
Detection and Annoyance
The same aircraft taking off may have a very different effect on different people, even in neighbouring houses. Both may detect it, but while one is undisturbed by it - perhaps because they have the television or radio on, or are simply accustomed to the noise - the other may find it highly annoying.
From a noise control perspective what matters is the cause of the annoyance. If it is the presence of the noise itself that produces direct and immediate annoyance, then reducing its level might do little to change the reaction. On the other hand, if annoyance is related to the intensity of the noise, then reducing it would help.
Disruption of work and activity (including schooling)
Many people feel that a quiet environment is needed for tasks that depend on being able to hear information, especially those involving mental concentration and creative activity. In particular, high levels of noise could be seen as very disruptive for children learning at school.
Many studies have sought to investigate this effect, and there is a growing body of evidence to suggest that exposure to high levels of noise can affect a child's reading ability, essentially because it disrupts their concentration.
It's well known that noise can interfere with sleep - that's why alarm clocks work! However, it's also possible to become accustomed to high levels of noise and so sleep through them, such as when you sleep on a plane or train.
It's also not just the volume of a noise that affects sleep - parents may well be woken by the stirring of a child, yet sleep through a thunderstorm. Sleep disturbance can also be caused by many factors other than noise, like stress, changes in light and other physiological reasons.
Despite extensive studies into the effects of noise on sleep, it is difficult to derive definitive noise exposure criteria governing sleep disturbance. What is clear, however, is that sleep disturbance is a significant cause of annoyance; so whether directly caused by noise or not, if people perceive a noise to be the reason for disturbed sleep they are more likely to be annoyed by it.
The human ear can be exposed to high levels of noise in excess of around 120 dB for a short time without their hearing being permanently harmed. However, over long periods of time of regular lengthy exposure to sound levels over about 80 dB may cause permanent hearing damage or even loss.
The level of aircraft noise experienced at locations beyond airport boundaries is not likely to cause hearing damage.
Stress and Other Health Risks
One of the effects of noise that is hardest to assess is stress. It is known that noise can cause a variety of biological reflexes and responses, which are referred to as stress reactions. However, it is unclear to what extent these might lead to clinically recognisable disease following a period of exposure to noise.
There seems to be general consensus that environmental noise can affect subjective sleep quality and mood the next day,and has an acute impact on heart rate. Some studies have found that children who are chronically exposed to noise experience raised levels of stress, increased blood pressure and mental health effects; but overall, scientific literature to date has generally found that the evidence for long-term impacts on stress hormone levels is inconclusive.
NATS (National Air Traffic Control)
For departure noise infringements aircraft noise is monitored at 6.5km from the start of the aircraft’s roll on the runway. Some other noise monitors are often deployed elsewhere to supplement these measurements. But the expense of these monitors can limit the number of locations surveyed, meaning that we know less about the noise generated by a stepped climb, an offset track or weather effects for instance. Conversations based on facts become very difficult when the costs of establishing the facts cause deadlock.
NATS say on their website that they are looking into new ways of measuring and dealing with noise. The information they present is dated 2014 and expreses intentions rather than achieved results.
They claim to be working with “a UK-based innovator in environmental sensing equipment, Envirowatch. Through their expertise and experience, we have jointly developed a self-powered sensor unit that is capable of being deployed wherever necessary to measure noise. These low-cost units require nothing more than daylight, passively gathering the facts under any flight path in both rural and urban neighbourhoods, and can also be used for many other noise gathering purposes in respect of road and rail transport links.”
What does this mean for the future?
The NATS website looks at what might be the implications for the future management of aircraft movement to and from airports. They offer the following examples of what might happen and then go on to propose how they will deal with noise related issues in the future.
Approaches and departure routes that track the major ground-based noise sources so that no-one notices? Or can we weave a path between the major population centres with aircraft climbing predictably without the on-off noise generated by a stepped climb? Can we optimise fleet and route schedules so that the quietest aircraft operate in the quietest times of the day?
Noise complaints for flights operating in and out of airports generally come from numerous locations, from residents inside and outside of any reported noise contours. As an industry that seeks to deliver sustainable growth in traffic whilst maintaining harmonious relationships with our neighbours, we should be striving to innovate noise measurement, to make the best decisions we can based on facts, not theory or modelling of noise.
NATS is researching new measurement techniques with Stansted Airport, where precision navigation trials are under way in parallel with traditional departure routes. The data we gather from this will inform future designs, by promoting fact-based evidence alongside the concerns of residents to ensure that we can deliver the best possible solutions.
London Stansted Airport’s (LSA) website gives details of how they monitor aircraft noise around the airport, the weblink is: https://www.stanstedairport.com/community/noise/noise-in-your-area/noise-monitoring-reports/
Aircraft noise is recorded at take off by fixed noise monitors which are located underneath the departure flight paths.
In addition, LSA have mobile noise monitoring equipment which is used to measure the noise levels in the communities close to the airport and assess how the impact may have changed over time.
As well as fixed noise monitors located under flight departure paths LSA, using mobile noise monitoring equipment, carry out one off noise monitoring studies in various localities around the airport.
To quote the web site:
Our monitors capture all noise in the vicinity for a three-month period, and by analysing the actual tracks of Stansted’s aircraft movements for that same period, we can identify the noise that relates to a Stansted aircraft movement and noise that does not. All work is carried out by an independent noise consultant who then compiles a report on the findings. These mobile noise monitor reports are given to the relevant Council for each area, as well as the local MP. London Stansted has a rolling program of sites where the monitors are placed and this enables us to establish trends in noise levels within the local community.
The website details these locations. Starting in 2006, 15 reports for different localities are listed. The most recent, for 2018, was carried out near Stebbing.
SSE (Stop Stansted Expansion) has a useful form obtainable on line http://stopstanstedexpansion.com/noise_complaint_form.asp
There are also helpful notes on their website http://stopstanstedexpansion.com/how_to_complain.html
Mike Begley (Councillor) Rayne Parish Council