The problem isn't the engine itself; that is actually relatively quiet. It's the rotors that make the classic "whup-whup" sound.
问题不在于相对来说更安静的发动机，而在于发出经典的“呼呼”声的旋翼。
The same principles can be applied to quiet down a jet engine or silence the open bays of a military craft.
同样的原理可用来使喷气发动机变得安静或使军用飞机在打开舱门时变得安静。
The same principles can be applied to quiet down a jet engine or silence the open bays of a military craft.
同样的原理可用来使喷气发动机变得安静或使军用飞机在打开舱门时变得安静。
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