[citation needed] Part of the study was to examine if a steeper continuous descent into an airport would reduce approach noise levels.
A major part of the study was to develop jetliner and engine designs that could meet the SAI objectives.
Because the blended wing is too shallow to accommodate twin engines, a four-engine configuration was proposed.
The favoured engine configuration was a turbofan with very low specific thrust, i.e. very high ratio of bypass air.
Furthermore, acoustic treatment in the intake and exhaust ducting can minimize turbomachinery noise.