The Quiet Technology Demonstrator 2 (QTD2)research and development program was completed in November 2005. A 777-300ER with GE90-115B engines, already the quietest airplane in its class, was fitted with eight different noise-reduction engine inlet and exhaust combinations on the right wing, and the baseline production engine on the left wing. Fan and engine-core chevron exhaust configurations achieved as much as a two-decibel improvement -- a significant community noise reduction. Because jet noise is generated by the jet wake -- extending nearly 50 feet behind the engine -- any reduction is considered a significant achievement. In addition, the low-frequency rumble heard in the aft cabin by passengers during cruise was reduced by up to four to six decibels.