P wave is just a pure pressure wave.

P波只是一种纯粹的压力波。

A Fourier transform is a way of decomposing a signal into pure sine waves, each with its own amplitude and frequency that add to make it up.

傅里叶变换是一种将信号分解为纯正弦波的方法，每个正弦波都有自己的振幅和频率， 相加而成。