A radius of a cylindrical speaker (source) oscillates harmonically. The oscillations produce sound waves in the surrounding air. The animation visualizes these density variations. The speaker can be at rest or move with respect to the surrounding air. You can change the ratio (v_source/v_sound) of the speed of the source to the speed of sound and the wavelength of the sound waves that are produced. You can also pause the animation to look at a snapshot. Clicking anywhere on the animation displays the scaled y and z-coordinates of the point that was clicked in meter and the scaled time it was clicked in milliseconds. (The animation does not run in real space or real time.)