Sound travels through air as a series of waves of compressed air.
Therefore, the interaction of these waves with a medium in its path causes vibrations and these sound waves can be converted into a more visible form. For example, an extremely thin and flexible membrane placed in direct contact with sound waves can cause it to flex outward like a balloon. This can be seen in the window demonstration. Select a wave form from the four provided and click on the button to see the effect of such a sound wave. Press to Send, or to Start over.