This free download uses the microphone in your computer (or you can use a plug in microphone for better quality) to detect sounds and instantly displays the sound waves on the screen. This would be a great tool to illustrate pitch and loudness, so they can make connections to the wave behavior.
That is a great idea. I appreciate the fact that this is a truly interactive generic resource and can actually respond to stimuli in your room as opposed to being a detached simulation.