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by mhandley
3898 days ago
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Yes, but why is a high bypass turbofan quieter? If I understood correctly, it's because most of the thrust comes from the large slow moving fan, so you don't need to blast nearly so much air through the turbine as a turbojet to get the same thrust. The whole purpose of decoupling the fans is to give you an even higher bypass ratio - two or three large electric fans driven from one turbine can have a larger swept area than a single large geared turbofan, so can run slower for the same thrust, and hence be quieter. |
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The noise comes from high speed air alongside slow moving air. A high bypass fan moves more air at slower speed to get the same push. The slower speed means less noise.