Speech signal processing - concept (4): Fourier transform, short-time Fourier transform, wavelet transform

From Fourier transform to wavelet transform , It is not a completely abstract thing , It can be said vividly . Wavelet transform has definite physical meaning , If we look at the problems faced when it was put forward , Can sort out very clear ideas .

Now I'll follow Fourier –> The short-time Fourier transform –> The order of wavelet transform , Tell me why wavelet appears 、 What is the idea of wavelet .（ Anyway, what the subject requires is a popular image , Not short , I hope it won't be too long ..）

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Reference material ：
Easy to understand Fourier transform 、 Short time Fourier transform and wavelet transform