The diagram is a screen shot from audio-editing software showing a graphical display of sounds. In this display the horizontal axis represents time. The sounds are shown as solid blocks of green. The height of the block represents the sound’s amplitude and its width represents its duration.
The diagram shows two blocks of sound, with a gap between them. The first block of sound has a large amplitude and a relatively long duration. Its duration is actually one second, but it occupies most of the diagram. This block is labelled ‘loud 632 hertz tone’. After this comes a short gap of silence labelled ‘gap’. This is followed by a short, low-amplitude burst of sound labelled ‘quieter 632 hertz tone’.