首先讨论了舰船辐射噪声的产生机理、构成和频率特性，指出螺旋桨噪声的振幅存在周期性调制。

First, the generation mechanism, components and frequency characteristic of radiated noise of naval ships are studied. There exists periodical modulation for the amplitude of propeller noise.

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接着，更多的信息表示通常是更好的也许要代表你的时间序列的一些基本特征，如频率特性的定义，振幅等。

Simplier, more informative representation is often much better Maybe try to represent your time series as some general features, like sime frequencies characteristics, amplitudes etc.

youdao

接着，更多的信息表示通常是更好的也许要代表你的时间序列的一些基本特征，如频率特性的定义，振幅等。

Simplier, more informative representation is often much better Maybe try to represent your time series as some general features, like sime frequencies characteristics, amplitudes etc.

youdao