A spectrogram analyses a speechwave into its frequency components. This allows us to see more detail about the articulation of the sounds. A spectrogram is rather like a graph. The vertical axis shows frequency (in Hertz), and the horizontal axis shows time (in milliseconds). The black marks show whether a component at that frequency is present at that time.
Here is an expanded spectrogram of part of our sentence, Notice that you see both vertical and horizontal lines on a spectrogram. The vertical lines relate to the opening and closing of the vocal folds. We can estimate the pitch of the sound from these can you figure out how? The horizontal lines are called formants. Try the ‘vowels’ button below to learn more about formants.