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The United States aviation industry is a significant contributor to the nation's economy,

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boasting annual sales in excess of $36 billion and providing nearly 1 million jobs.

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However, with all of these benefits, one major drawback continues to be aircraft noise.

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In an effort to help alleviate excessive noise, NASA has developed the Quiet Aircraft Technology Program.

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This program is finding new and innovative ways to reduce noise created by aircraft.

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Jennifer Pulley finds out more.

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Noise generated by aircraft is already a major issue in airport neighbor communities.

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As airports expand to increase productivity and capacity, the noise issue will become even more critical.

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Noisy aircraft not only affect the people in communities surrounding the airport,

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but also the crew and passengers inside the planes.

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In an attempt to solve many of the noise issues associated with aircraft,

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NASA has embarked on an intriguing new mission to quiet our skies,

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called the Quiet Aircraft Technology Program, or QAT.

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This program will develop technologies to reduce aircraft noise by 50% in five years

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and begin working on the technologies to reduce aircraft noise by 75% in the next 20 years.

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I spoke with Andy Powell at NASA Langley Research Center to find out more.

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On takeoff, most of the noise that you hear is due to the engine,

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both the fan in the front of the engine and the jet exhaust noise out of the rear engine.

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And what most people don't know is that on landing,

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a lot of the noise that you hear is actually due to the airframe passing through the air itself.

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This is because on landing, the engine power is cut back

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and a lot of parts of the aircraft are extended into the airflow and create turbulence.

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Now the major sources of this airframe noise is the landing gear,

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the flaps on the trailing edges, and slats on the leading edges of the wings.

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In a recent government survey, noise was listed as the greatest environmental concern at airports.

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It is estimated that in the last 20 years,

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approximately $4 billion has been spent on or around airports to reduce noise pollution.

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This includes adding sound insulation to homes and schools in close proximity to an airport.

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Unfortunately, these techniques only help if you are inside an insulated building.

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Researchers at NASA realize that in order to fix the noise problem,

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they must first start at the source, the planes themselves.

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By designing and testing low-noise-producing aircraft parts and structures,

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NASA researchers are developing the technologies to reduce aircraft noise by half in five years

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and by as much as three-fourths by the year 2020.

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So what are some of the things you're working on here at NASA to make aircraft quieter?

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First, we do studies to look at the sources of noise to try to determine which are the dominant sources

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so that we can know which sources can work on the hardest.

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Then we do other studies to try to determine the physical phenomena that are creating the noises

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and what we can do to reduce the levels.

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And then we go out and test concepts either in wind tunnels or in the laboratory

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and in some cases in actual flight tests to validate those concepts.

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One of the things that we're doing is to look at advanced fairings to put around the landing gear

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to smooth the flow around the landing gear so that you don't have as much turbulence

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and therefore reduce the noise.

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We're also looking at other fairings that we can put on the slats

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so that you don't have side edges to create noise.

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We're also modifying the fan blades so that they're actually quieter from the design of the fan blades.

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If you can smooth the airflow around these parts,

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then reducing that turbulence will reduce the noise considerably.

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Andy, what about the exhaust noise coming out of an aircraft?

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Okay, well, one of the things that we did was look at what we call chevron nozzles.

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These are actually scallops in the back of the exhaust pipes, essentially, of the aircraft.

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And as hot exhaust gases come out of an aircraft engine,

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then they mix with the surrounding air and this turbulence, when they're mixing,

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creates a lot of the noise that you hear.

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Now, by putting these chevrons along the edges,

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we're changing the shape of the turbulence so that you raise it to a higher frequency,

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which then is absorbed more by the atmosphere than the low-frequency, normal jet noise.

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The chevron nozzles have actually been test flown full-scale on a major aircraft,

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and we expect that these will actually be coming in on the production of aircraft engines in the very near future.

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We've talked about engine and airframe noise.

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Are there other ways to reduce noise without major design alterations to an airplane?

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Yes, we're actually looking at new ways to fly the aircraft around the airport

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so that they've minimized the exposure of people to the aircraft noise.

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For instance, around a lot of airports, they fly noise abatement procedures

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to get the flights away from schools and houses.

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But in some situations, if the wind is blowing,

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these flight paths may not be the optimum flight path

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because of the effects that wind has on the sound propagation.

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So we're doing studies on improving the prediction of sound propagation

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to include the effects of wind, weather,

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and this way we hope that we will be able to reduce the noise and have the planes fly optimal paths.

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And finally, what are your overall hopes for the QAT program?

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Well, one of the three elements in NASA's vision is to improve life here on planet Earth.

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And we think through this Quiet Aircraft Technology Program,

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we're making a major contribution to improving the life for people

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and the environment around airports, both in the nation and throughout the world.

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Ultimately, NASA would like to reduce airport noise

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so that no one outside the airport boundary is adversely affected.