First, as a warm up, open this "toy" spectrogram from Chrome music lab: httpszlfmusiclab.chromeexperiments.comepectrogram! It doesn't have an axis labels, but it will still give you some intuition for the frequency content of several examples. Click on an individual button to hear a sample and see the corresponding spectrogram. Here frequency is plotted vertically, and amplitude is color coded in the 3rd dimension, white the horizontal axis is just time, so you can see the "history" of what was heard . You can also click and drag to create single frequency sounds (the mouse arrow button) or choose the microphone on your own device to make your own sounds to view