You’re a teacher, so you know how loud kids are. (Or, if you’re not a teacher, why are you reading a website dedicated solely to grade-school science experiments, weirdo? [Thanks for reading, BTdubs.]) Where does all that sound come from? And how does that sound achieve different tones and/or pitches? This Demo Science science demo will show kids just how the heck they’re so loud all the time.
Blowin’ In the Wind
For this experiment, all you’ll need is one 2” by 2” square of cellophane or plastic wrap for each student. Instruct your students on the correct procedure, which is this:
Tightly stretch the cellophane, holding it taut with betwixt your thumbs and index fingers. Hold your hands, and therefore the plastic wrap, directly in front of your face with the cellophane right in front of your lips. Then, blow as hard and as fast as you can, aiming directly at the edge of the plastic wrap. Keep your lips close together so as to maintain a thin stream of air. (You don’t need to blow super hard; you’re not trying to fire a pneumatic rivet nut tool or anything.)
If done correctly, this should produce a high pitched sound, not unlike your students talking at any given moment, because they’re most likely at every given moment. If high pitched sounds are not forthcoming, adjust the distance betwixt your mouth and the cellophane until it works.
Note: Instead of plastic wrap, this demo can also be performed using two sheets of notebook paper stacked atop each other, with the bottom sheet sticking out toward you about 1/2” extra. Just blow betwixt them! This method will produce a sound like a small, sickly duck.
Shut Up & Science, Kevin
So, just how does this work? Well, the thin stream of air blasting through your Chapsticked lips causes the cellophane (or notebook paper) to vibrate at high speeds. This vibration causes sound, and the faster the vibrations, the higher the tone of the sound.