The simplest way to dampen a helicopter's noise is to increase the Angle of the rotor's blades, also called the pitch, and slow them down.

要降低噪音，最简单的方法是增大旋翼桨叶的夹角，也叫“节距”，或是降低转速。

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The level of noise we hear also depends on the Angle and distance of the shell from the ear.

我们听到声音的大小同时也取决于贝壳与耳朵的角度及距离。

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Air compressor noise is the main noise source. From the Angle of air flow noise, can be briefly analyzes the following.

气流噪音是空压机的主要噪声源。从气流噪声的角度，可以简要分析如下。

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