Noise Research

Future Outlook: A Quieter Airplane Design

Can airplanes be redesigned to be virtually silent? MIT and Cambridge universities are working to create an aircraft that cannot be heard outside of airport boundaries. This would reduce current noise levels by a substantial 25 decibels.

To accomplish their goal, the "Silent Aircraft Initiative" team plans to reduce airplane noise during both takeoff and landing. Noise from takeoff is primarily caused by a plane's engine. To reduce noise on takeoff, the team is working on a new engine design.

Landing noise is produced by a plane's airframe as well as its engine. Flaps and slats are a large source of noise produced by the airframe. Therefore, the new plane designs have no flaps or slats (See How Aircraft Work).

Slower landings can also significantly reduce landing noise. Therefore, the plane's body shape is designed to accommodate landings at lower speeds. The plane's engine is designed for both slower takeoffs and slower landings.

The total area of the new airplane's exhaust is doubled as compared to today's jet engines. A larger engine could increase drag. However, the new design changes the placement of the engine, embedding it within the aircraft. The engine intakes are positioned on the upper surface of the plane. Thus, the plane itself shields the ground from engine noise.

Not only is the new airplane designed to be quieter, but it also more fuel efficient. In this new design, the plane's wings are merged with its fuselage (the body of the plane). The new shape of the airframe has a high ratio of lift to drag forces. Thus, the "silent aircraft" is designed to carry 215 passengers with a 124 passenger-miles per gallon fuel efficiency. Standard jets reach fuel efficiencies of only 100 passenger-miles per gallon or less.

The "Silent Aircraft Initiative" is run by 40 researchers from MIT and Cambridge and receives help from 30 companies. Still, the final "silent aircraft" product is not scheduled to be completed until the year 2030. Even after its completion, its commercial success is not guaranteed.

There is more information on the Silent Aircraft Initiative from the Cambridge MIT Institute Partnership Programme.

For a quick look at Silent Aircraft, check out this video

Reference Citations:

"The Silent Aircraft Initiative (SAI)." The Cambridge-MIT Institute. 12 November 2006.

Associated Press, et. al. "Silent plane would cut airport noise." CNN.com. 7 November 2006. 12 November 2006.

Glossary Words:

decibel, drag, flaps, fuselage, jet, noise, ratio of lift to drag forces, slats

For definitions of words used in this section go to the NoiseQuest Glossary of Terms.