Aircraft noise causes much more annoyance than previously thought, according to a study for the Department for Transport which the Government is attempting to conceal while it plans the expansion of Heathrow.

The existing method of measuring aircraft noise, adopted a quarter of a century ago, is too narrow and outdated, the study concludes. It fails to take account either of the huge growth in the number of flights or the public’s growing demand for quietness.

While individual aircraft have become quieter, the number of flights at Heathrow has grown from 273,000 in 1982 to 477,000 last year.

The study also found that aircraft noise causes greater annoyance to people on higher incomes, those in the social groups A and B and those aged 35 to 64. The current method takes none of these factors into account.

The Attitudes to Noise from Aviation Sources in England (Anase) study, a draft copy of which has been obtained by The Times, undermines the case for building a third runway at Heathrow. The runway, which the Government has said should open between 2015 and 2020, would create new flight paths and result in an extra 500 flights a day over London.

The 2003 aviation White Paper pledged that the runway would only go ahead if it resulted in “no net increase” to the size of the area around Heathrow affected by 57 decibels of aircraft noise, the level deemed to mark “the onset of significant community annoyance”. But the new study suggests that significant annoyance starts at around 50 decibels.

While there are 258,000 residents inside the 57-decibel area, ten times that number live inside the 50-decibel area.

Jim Fitzpatrick, the Aviation Minister, last week rejected calls to publish the study early in a letter to the “2M” group of 12 local authorities covering two million residents living under Heathrow’s flight paths.

He claimed that the study had yet to be finalised, even though it was ordered six years ago and the draft reveals that the DfT had seen a copy three months ago, on July 5. Mr Fitzpatrick wrote: “It would be premature to suggest that the report will lead to any change in approach – we shall want to reflect on it . . . We would not accept that the launch of the Heathrow consultation cannot precede Anase.”

His attempt to downplay the significance of the study contrasts with the commitment given in 2001 by the then Aviation Minister, Bob Ainsworth, when he commissioned the study, saying at the time: “This study underlines the Government’s commitment to underpin our policy on aircraft noise by substantial research that commands the widest possible confidence.”

A spokesman for the 2M group said: “It is outrageous for the Government to hide this study, which reveals how the impact of aircraft noise has been seriously underestimated. They are trying sneak through the third runway consultation without giving the public the full facts.”

The study concludes: “At the same level of aircraft noise exposure, people are more annoyed in 2005 than they were in 1982 . . . People today have higher expectations of their rights to a peaceful and harmonious living environment and are more openly critical of policy-making and government, than people at the beginning of the 1980s.”

The study found that people found flights between 11pm and 3am were 80 per cent more annoying than those during the day. But flights between 3am and 7am were only 35 per cent more annoying. The number of Heathrow flights between 11.30pm and 6am is currently restricted to about 16 a night.

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