Anyone who lives near an airport knows jets can be very loud! When jets take off, their engines can make so much noise that people living near the airport must stop conversations until the jet has flown away from them. Jets are loud when they land as air hits and moves across parts of the jet's airframe.

NASA is working to quiet the noise jets make as they fly - especially during takeoffs and landings. The Quiet Aircraft Technology Program hopes to reduce the noise jets create by 75% over the next 25 years. This should make everyone feel - and hear - much better!

The loudest sounds are created by a jet's engines during takeoff. Air is forced through the engine which produces noise as the air moves. The fan also creates noise from the engine as it turns which forces air to pass through the engine. Obviously, jet engines are needed for an aircraft to fly quickly between two cities. NASA is working hard to redesign engines and their parts which will produce quieter takeoffs.

Noise is also created during landings when air moves across the airframe (body). Research is being conducted to see how to let air move more easily past wing flaps and landing gear. These are two parts of the airframe that produce noise when they are hit by moving air.

Passengers inside the aircraft are also affected by the noise created from air hitting the airframe as well as engine noise. A passenger can always wear headphones which will block much of the noise.

An "absorber" has been added to some aircraft to help block out interior noise. It acts like a tuning fork that vibrates and produces sound waves which are exactly opposite of the sound waves produced as "noise" in the aircraft. These two opposite waves cancel out each other. The process works like a jump rope held by two people. If one person moves his arm up (and the rope upward) while the other person moves his arm down (and the rope downward), then the rope between them gets still. This means that any wave motion in the rope between them is cancelled.

As airplanes are replaced, they should become quieter with design changes. You can thank NASA's Quiet Aircraft Technology Program for taking the lead in reducing jet noise.