pulsewidth?

So here the plot is coming as pulse width, as something related to envelope, Fs
Fs... if frequency?

Well the plot units are Frequency over Time
So like the x-axis on the two plots we had previously...

I believe that's why a spectrogram is... which is something that shows the progress of time...
or the order that the numbers were played...
or the frequencies that were... in this case, solved by using the envelope algorithm on tones, and then quantifying it with that 80 and ploting that Frequency envelop of tones, with Fs... weird...
so whats up with the f


when was it even used?