Update README for spectrogram control

README.md

@@ -98,7 +98,16 @@ You can click on `resize plot` to compute one resize for the current layout (tak
 By clicking on `Play current segment`, the sound of the current signal segment will be played.
 Note that while the sound is played, the interface becomes irresponsive. 
 As stated above, the audio player used by pydub require additional libraries.
-If you're using this script on a remote server, the sound might be play over there or not work depending on the method you use to access said server. 
+If you're using this script on a remote server, the sound might be play over there or not work depending on the method you use to access said server.
+
+#### Change the spectrogram parameters
+The four buttons on the left of the groups of plots can be used to change the spectrograms' settings.
+
+The two top buttons are used to increase/decrease the maximum frequency of the spectrogram.
+Frequency bins that are above the nyquist frequency are will be displayed entirely white.
+
+The two bottom buttons are used to change the size of the FFT window used by the spectrogram.
+The number of bin indicated by each button will be the size of this window after click on the corresponding button.
 
 ### Output