Analysis of the helicopter noise signature.

对空气中的直升机噪声进行了分析。

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In the end, this paper calculates the noise of hovering rotors that is basic researching work for helicopter noise reduction.

本文最后数值模拟直升机悬停旋翼的气动噪声，为直升机降噪研究打下一定的基础。

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No sound whatsoever, but the noise of the radio and the helicopter.

没有任何声音，除了广播和直升机的噪声。

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The witness said he did not hear any irregular engine noise when the helicopter went past and the height and speed of the craft were normal.

BBC: Colin McRae's neighbour describes helicopter crash

On 1 December the man was traced when rescuers listened to the background noise of the helicopter travelling back and forth along the mountainside to pinpoint his location.

BBC: Helicopter over Snowdonia

Whether blocking out the loud noise made by a deadly attack helicopter, the construction work just outside the home or any other ambient sounds, gamers will hear nothing but the sweet, immersive sounds of ownage, destruction and victory.

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