|MadSci Network: Physics
Hi J Clark,
Why do snapping fingers make a noise? Well, first we have to think about what part of the finger snapping motion causes the sound. Your students might be interested in doing an experiment to observe that it is in fact the impact of your finger on your palm that causes the "snap". The next question, which you alluded to in your message, is how (and why) we hear this impact. Why do claps make a sound, for that matter? I suspect that this is an oversimplification, but one way of explaining it is that when your palms (or finger and palm) come together quickly, the air between them has to get away in a hurry. This causes a pressure wave –where air molecules get scrunched together– that travels outward from the source. Sound is a pressure wave so when it reaches our ears we hear a "snap".
Try the links in the MadSci Library for more information on Physics.