This website provides an animated QuickTime video showing how sound waves work. The video is available in different formats for Mac and PC and is customized for different modem speeds. You can learn that sound is made when air molecules vibrate and move in a pattern called waves, or sound waves.
This site provides a real world focus on a phenomenon that is more or less invisible to kids—sound waves. This video can be used as a quick introduction to the concept of sound waves. It would probably make a good motivation activity for a lesson on sound. Note: Since sound can be intrusive in a classroom setting, it is recommended that students use headphones. This activity can be done along with How Loud is Too Loud? The content is best suited for students in grades 4-6.