增加旋翼桨叶数量也是一种方法，这使得每片桨叶负载的直升机重量降低了，因此产生的噪音更小。
Then there's increasing the number of rotor blades. This helps because each additional blade carries less of the weight of the helicopter, and thus produces less noise.
与在高空飞行的飞机不同，直升机不容易被雷达发现，因为它的飞行高度较低，且常常被地形所隐藏，因此最大的问题是噪音。
Unlike high altitude aircraft, helicopters aren't so vulnerable to being seen by radar, as they fly low and are often hidden by the terrain. The big issue is the sound.
最后一天的早上，学校举办了一场特殊的聚会，但盘旋在头顶的直升机让我们难以听到噪音以外的其他声音。
We had a special assembly that final morning but it was hard to hear with the noise of helicopters overhead.
如果他们真的想要隐形直升机，他们应该创造一个类似于科曼奇能够覆盖住螺旋桨并能提供更大的扭矩而且能缩减噪音。
If they really wanted a 'stealth' helicopter they should have looked into creating something similar to the Comanche which has a covered fan that provides more torque while reducing noise.
如果他们真的想要隐形直升机，他们应该创造一个类似于科曼奇能够覆盖住螺旋桨并能提供更大的扭矩而且能缩减噪音。
If they really wanted a 'stealth' helicopter they should have looked into creating something similar to the Comanche which has a covered fan that provides more torque while reducing noise.
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