在理解相位噪声之前，我们先从理想的单音开始。 理想单音信号，可以用cos函数来表示，它的频谱就是一根线，如下图所示。 但实际上的频谱并不是一根那么纯净的谱线，而是有噪声分布在周围。

In this first programme in a special series on English pronunciation, Alice Castle and Wang Fei find out what sounds are often wrongly pronounced by Chinese learners of English and how they can ...