How to see the amplitude of each frequency?
As I have not had enough reputation to comment, I will provide some of my interpretation of your question (Don't need to accept my answer).

It looks like that you want a spectrogram represented by a 500$\times$22000 matrix. This relates to the number of time and frequency slots. The number of time slots (columns) is determined by the sample number of the given signal. The number of frequency slots (rows) is determined by number of FFT output, which you can adjust by methods such as zero padding.

If you want to get better-looking spectrogram, you might need to adjust the window that is used in performing STFT (or maybe more overlapping in STFT). However, sometimes you just cannot get satisfying resolutions as the time-frequency resolutions are bound to the uncertainty principle. This is decided by your time-domain samples.