Aircraft vs road vs train noise: which bothers people most?

If you are choosing between a flat on a main road, a house by a railway and a cottage under a flight path, the decibel figures alone will mislead you. The same average level does not bother people equally, and aircraft come out worst by a wide margin.

Aircraft noise bothers people most, level for level

The World Health Organization's 2018 guidelines for Europe were built on a systematic review of surveys around roads, railways and airports. For each source, the review worked out what share of people are highly annoyed at a given average noise level, measured in Lden (a 24-hour average with extra weight on evening and night noise). These are the figures from the guidelines' exposure-response curves:

At night the gap is wider. At 40 dB Lnight outside the home, about 2% of people near roads or railways say their sleep is badly disturbed, against 11% near airports. At 50 dB Lnight it is 4% for roads, 6% for railways and 20% for aircraft.

Other research points the same way. The FAA's national survey around 20 US airports, published in 2021, found 60% to 71% of people highly annoyed at 65 dB DNL, against 12% on the older curve behind FAA policy.

The WHO guideline levels for each source

The WHO set its guideline levels close to where about one person in ten is highly annoyed, and where about 3% report their sleep badly disturbed. Because aircraft noise reaches those points at lower levels, its guideline is lower.

All six are strong recommendations. For aircraft at night, the WHO noted that even 40 dB Lnight leaves about 11% highly sleep-disturbed, more than it aimed for, so the value may not fully protect health. Our guide to the WHO aircraft noise guidelines explains how the levels were chosen and what they mean for a home.

Why aircraft noise is harder to live with

The surveys measure what people report; they do not fully explain it. But several differences between the sources are clear.

It comes from above

Road and rail noise comes from one side. Houses, walls and barriers can block it, and a bedroom at the back of the house can be much quieter than one at the front. The WHO guidelines note that having a quiet side of the home reduces annoyance and sleep disturbance from road traffic. A plane overhead reaches the garden, the roof and every side of the house at once, so there is nowhere quieter to retreat to.

It comes in loud bursts

Busy road traffic is a fairly steady sound. Aircraft noise is a series of separate events: quiet, then a jet passing low, then quiet again. An average spreads those peaks across the whole day. The WHO noted that average levels may miss some effects of aircraft noise, such as being woken, and that counting noise events may be better suited.

It changes from day to day

Traffic on a main road is much the same on Tuesday as on Wednesday. Aircraft follow the wind, and airports turn their traffic round when it changes, so the same street can be loud for a week and then quiet. At Kew Green, 10 km from Heathrow, our sample report counts 92 loud landings a day when the wind is from the west and 4 loud flights a day when it is from the east.

Change makes it worse

The review behind the WHO guidelines found that people living near airports whose operations were changing reported more annoyance than people near airports where nothing was changing. It also found higher annoyance in surveys since 2000 than in older ones at the same noise levels, most clearly for aircraft. The reasons are not fully understood; changes in how surveys ask the question may explain part of it.

Road noise still affects far more people

None of this means aircraft are Europe's biggest noise problem by numbers. In the 2022 round of EU noise mapping, the European Environment Agency counted about 92 million people exposed to road traffic noise of 55 dB Lden or more, 18 million to railway noise and 2.6 million to aircraft noise. Road traffic is by far the most widespread source; aircraft affect fewer people, but more intensely at each decibel.

What this means when comparing homes

Use each source's own yardstick. On the WHO figures, a home with 60 dB Lden from road traffic would leave about 15% of people highly annoyed, and a home with 55 dB Lden from aircraft about 27%. A quieter number on paper can be the harder place to live.

• Look at each map separately. In the EU, strategic noise maps cover major roads, major railways and major airports, source by source. Compare each against its own guideline level, not against each other.
• For roads and railways, check the layout. Which way do the bedrooms face? Is there a quiet side, a wall or a row of buildings between the house and the traffic? For railways, ask how many trains run at night, including freight.
• For aircraft, count the flights. An average hides how many loud planes pass, when, and on which days. Find out how many fly over on a typical day in each runway direction, and how many at night. Our guide to checking aircraft noise before buying a house covers the checks.
• Visit at the right time. A busy road sounds much the same on any visit. A flight path may be silent the day you view the house, so visit when the wind sends planes over it.

The same number of decibels means different things depending on where the noise comes from. For a home under a flight path, the most useful figure is not the average but the count: how many planes a day are loud enough to interrupt a conversation, and how many of them at night.