Cranfield Airport’s plan may impact on local schools [School being in 60dBA Leq,16hr band corrected after Cranfield University Reply 16/2/18]
An increase in air traffic noise at Cranfield Airport might have an impact on local children’s reading age and memory.
One piece of research, the RANCH (Road traffic and Aircraft Noise and children’s Cognition & Health) Study, found that a 5dB increase in noise exposure is associated with a two-month delay in learning in UK primary school children.
AEF director, Tim Johnson, said:
“We think this is an important issue that, alongside the other health impacts of exposure to aircraft noise, needs to be addressed by the Government and the industry.
“While its common to assess the number of people living within noise contours, noise sensitive buildings like churches, hospitals and schools are often overlooked.”
Children are thought to be vulnerable to noise as they are still developing physically and cognitively.
Cognitive impairment by noise in children is defined by the World Health Organization (WHO) as a
“reduction in cognitive ability in school-age children that occurs while the noise exposure persists and will persist for some time after the cessation of the noise exposure”.
It is not clear which has the greatest effect on children’s learning. It could be the overall dose of sound energy, the number of events, or the maximum noise level.
Cranfield Airport’s planning application does acknowledge an increase in air traffic noise above the current level. Its Noise and Vibration Annex of its planning application states:
“The impacts [of air traffic noise] will be similar to levels of noise to those historically experienced.”
Noise is averaged over 16 hours
The noise generated by airports is measured in decibels. A decibel is a ratio of how much acoustical energy can be heard compared to some “reference level”. This is a logarithmic scale and there are also various scales of decibels. With human hearing the dBA scale is used.
The noise from a aircraft engine might be given in dBA, however, noise from transport sources (road, rail and air) is measured in dB LAeq,16hr (or dBA Leq,16hr).
This works by averaging out the sound energy from each noise event and presenting it as if it were a continuous noise over the measurement period. In this case, over 16 hours.
The scale dB LAeq,16hr is the official aircraft noise metric in the UK. Johnson, said:
“So airports would be expected to show the impact using this metric. However, no one experiences continuous average noise.
“In reality its a series of (sporadic or more frequent) noise events with periods in between when you can only hear the background noise.”
As this is the average noise over the 16 hours, many communities argue that additional metrics are needed. Such as the maximum noise level that will be experienced, or the number of noise events above a given dBA level.
The WHO sets the onset threshold of the effect on children’s memory and learning at 50dBA Leq,16hr. It also recommends that noise in school outdoor playgrounds should not exceed 55 dBA Leq, 16hr.
Cranfield Airport’s Noise and Vibration Annex, shows that the school in Braeburn Way will be in the 57dBA Leq,16hr band [AMENDED – removed 60dBA Leq,16hr band]. This above the WHO limit.
[Added 16/2/18] A spokesperson for Cranfield University said:
“The Government is responsible for considering World Health Organisation guidelines on community noise and developing UK policy. In making any application the airport follows the Government’s official policy on these matters.”
Annoyance threshold could be reduced
A Government-commissioned study into attitudes to aircraft noise, published in 2017, found that the threshold for the upturn in annoyance starts at 54dBA Leq,16hr rather than at 57dBA Leq,16hr.
The airport’s application uses the level stated by the Aviation Policy Framework (2013) at 57dBA Leq,16hr. It says:
“The Aviation Policy Framework states that it will continue to treat the 57dB LAeq 16 hour contour as the average level of daytime aircraft noise marking the approximate onset of significant community annoyance.
“However, this does not mean that all people within this contour will experience significant adverse effects from aircraft noise. Nor does it mean that no-one outside of this contour will consider themselves annoyed by aircraft noise.”
Is it reversible?
It is uncertain how the long-term effects of exposure to aircraft noise on cognitive development of children.
Some evidence suggests that the deficit in learning disappears if the child is no longer exposed to aircraft noise.
A study on the relocation of Munich airport found that the cognitive deficit associated with high levels of aircraft noise disappeared two years after the original airport’s closure.
New homes have been built closer to the runway
Since the Airport gained planning permission in 2008, new houses and the school have reduced the buffer between the runway and the village.
AEF Director, Tim Johnson, said:
“The [aviation] industry would probably agree as there is a constant frustration with local authorities who allow development just outside noise contours that could subsequently lead to a larger impacted population when the number of flights starts to increase.”
Children could be exposed to noise during all of the Airport’s operating hours
The Airport says that it will be operating between 06:00 and 22:00 (although it also reminds us that it is a 24/7 airport). It is possible that children living near the runway and attending the St Pauls site could hearing noise above the WHO threshold throughout the airport’s working day.
“I think it’s right that parents should be asking for more scrutiny of how the proposal will impact schools. Specifically, how many movements are likely to occur during school hours and what’s the maximum noise level of each overflight?
“Comparing this to background noise levels in the classroom should provide better information on the likely degree of intrusion and, depending on the answer, whether the problem can be ameliorated by better insulation of school buildings.”
[ADDED 16/2/18] The University spokesperson said:
“The responsibility of the design and planning approval for the school rests with the local planning authority. It is the responsibility of the local planning authority to ensure that the school will have been designed to account for it being built within 550m of the centreline of an active 24/7 airport, capable of receiving 150,000 movements per year and with specific recent pre-existing planning consent (2008) for expanding business jet operations in the future.
“It should be noted that the contours have been produced for a range of scenarios. For the phase one 2023 contours (which include existing movements and business jets at 14,500 movements) none of the school buildings nor any part of its grounds are expected to be within the 57dBA LAeq,16hr contour for this phase.”
[ADDED 16/2/18] The projected flight times and quantity of business flights are shown in the graph below. As can be seen the quantum of business aircraft will increase to an average of 2 per hour for phase 1 and approximately 5 per hour for phase 2.
“As demonstrated in the graph above, the proposed peak times for the airport will be outside of a school’s typical start and finish time.”
When asked if its Education Department is concerned that the Airport’s latest planning application might cause learning issues at the Church of England Academy St Paul Site, a spokesperson for Central Bedfordshire Council said:
“The Cranfield Air Park has not been operating the maximum number of flights under its existing permission. The maximum flights allowed at the site will form a baseline upon which noise assessments are made.
“The applicant has employed a separate noise consultant who has modelled the likely implications of an increased frequency of aviation movements. This has been presented to our Public Protection Team, who are considering the application on these grounds.
“The well-being of our residents is of upmost importance to the council, which is why noise assessments are part of the planning process. The results of these will be one of the many things we take into account before making any final decision.”
The University’s spokesperson said:
“The proposed increase in annual movements to 46,000 are significantly below the Airport’s permitted capacity of 150,000 movements. There can only be one aircraft arriving or departing at any one time due to there being only one runway. The noise level experienced on the ground is therefore from individual business jet aircraft.
“So for instance, having twice as many movements means the level of noise is experienced twice (but not simultaneously) and not 3dB higher as the contours would suggest. These aircraft already fly into and out of Cranfield and so the noise levels are already being experienced by the school.
“The airport is committed to producing a Noise Action Plan on an annual basis that will look at whether the airport continues to comply with current Government policy and what measures need to be taken, if any, to bring the airport in line.”
Comments about the Airport’s planning application can be submitted here.