MATLAB: How is audio data displayed

audioMATLABvideovideo processing

I have extracted an audio signal from a video now how do i see the contents of audio signal?

disp() or fprintf() or plot()

Or possibly you would like to create a spectrogram.

Because the loop condition is never satisfied and therefore nothing within it is ever executed. I think you meant to have,

while error>10^-4

You've overwritten f(1) when you set f(s2)=0; Replace your first stem line with the values directly:

stem(n_3, 4./(pi*s1).*sin(s1*pi/2), 'p')