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The global demand for air travel that carries humans is on the rise as well. That means many airports are experiencing growing pains and are looking to expand to fit in more flights and passengers. For example, London's Heathrow Airport - it's lobbied for years to build a new runway, but it faces stiff opposition from local residents who worry about noise. Christopher Werth reports from London.
(SOUNDBITE OF PLAYGROUND)
CHRISTOPHER WERTH, BYLINE: This is the sound of recess at Pippins Primary School. It's just one of dozens of schools around London's Heathrow. The students play, they kick a soccer ball and like clockwork, every 90 seconds, they hear this...
(SOUNDBITE OF AIRPLANE)
WERTH: Judging by the way that plane came through, I would say that you really are right under the flight path here.
JANET MILLS: Yes, it is very loud. It's as if you were standing on the runways.
WERTH: Janet Mills is a teacher at Pippins, and I asked her what it's like to teach right next door to one of the world's busiest airports.
MILLS: It's quite tricky because a large number of our parents are employed at Heathrow so we can't say it shouldn't be there, but obviously the noise - you're continually stopping, you know, we let the plane fly over and then we start our lesson again.
WERTH: Even then, students like 11-year-old James Tyler Brooks say it is very hard to hear both outside and inside the classroom.
JAMES TYLER BROOKS: It's really annoying because when you don't hear you can't learn because you don't know what the teacher is saying.
WERTH: Heathrow is rather unique in that over a quarter of all Europeans who suffer from aviation noise live right here below Heathrow's flight path. And if the airport has its way, that could get even bigger.
CHERYL MONK: Heathrow wants to expand. We want to be the U.K.'s hub airport.
WERTH: Cheryl Monk is with Heathrow Airport Holdings - the company that owns Heathrow. It wants to build an additional third runway to increase the number of flights in and out of the airport. And that is a very contentious proposal in Britain that's drawn large public protests. But Monk says Heathrow is at maximum capacity and she says that hurts London's ability to attract business to the U.K.
MONK: We are the world's busiest two runway airport so we want a third runway at Heathrow. And, yes, we know noise is an issue, that's why we're looking at ways we can reduce that noise.
WERTH: Heathrow collect millions of dollars in fines on louder aircraft to fund noise mitigation projects in the local community. At Pippins Primary School, work is underway on Heathrow's latest method for blocking sound, and it's unusual. Over the past few months, large white domes made from earthen adobe have sprung up on the school's playground. They may not help in the classroom, but they're meant to make playing outside at least a little quieter.
Oh, wow. So we're just entering what I guess is the main chamber of the dome, right?
JULIAN FAULKNER: Yeah. It's 13, 14 feet high and about 16 feet wide.
WERTH: Julian Faulkner, the designer, says the domes can cut aircraft noise by nearly a third.
FAULKNER: It's absolutely rock solid, you know, so that children can still go outside, enjoy the fresh air without being completely deafened.
WERTH: Heathrow plans to build domes at 21 schools at a total cost of $3 million. It's even printed glossy brochures that show grade-schoolers laughing and playing under the protection of the domes. And that really irks those opposed to Heathrow's expansions.
JOHN STEWART: Heathrow Airport have not been altogether honest as to why they're putting a lot of money into these domes.
WERTH: John Stewart is with the Heathrow Association for the Control of Aircraft Noise, a London-wide community group.
STEWART: When I see the images that Heathrow Airport use of the domes and always smiling cuddly children - what goes through my mind is, yes, that's nice for the children, but the real reason they're probably being put in is to try and soften up the residents in order to make a third runway at Heathrow more acceptable.
WERTH: Heathrow says local support for expansion is growing, but a final decision on expansion is at least a year away. For NPR News, I'm Christopher Werth, London.