Difference in frequency domain between mp3 and wav

I have plotted the frequency domain figure for mp3 and wav as shown in Figure below.

They are in dotted blue and dark orange respectively.

Why is there no difference which I thought the frequency of mp3 should be lower.

Thank you.

Answer 1

[Bjorn Gustavsson]

There are some small differences. You should also try to compare the spectrograms of the two signals, see the help for spectrogram. Are there big enough differences between the two audio-signals that you can hear it?

[Star Rats]

The spectrogram is also the same. mp3 is in 4MB while wav is in 25MB.

Is it hard to observe naked-eye?

[Bjorn Gustavsson]

For the power spectra try to plot the difference, and the ratio, same for the spectrogram. you can try to plot the ratio between the time-series as well, will you see any difference? Do you hear any differences?