Update README for spectrogram control

README.md

@@ -100,6 +100,15 @@ 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.
 
+#### 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
 
 Once done, the script will save the label in a HdF file (whose name depend on the options used).