This experiment comes from a question that I got from a subscriber. As I researched the question, it was even more interesting than I expected. It also seemed like a good excuse to eat lots of ice cream.
This experiment is something that we used do for fun when I was a kid. (No jokes about dinosaurs or the Dark Ages, please.) It was back in the days before video games and the internet. Back in the days when there were only 4 TV channels and you had to get up and turn the dial on the TV to change the channel. Even so, we still had lots of fun. This is a science trick that always amazes people.
This experiment is something that I ran into MANY years ago when I first began wearing glasses. If you wear glasses, then you know how challenging it can be to find your glasses if you have laid them down and can't remember where you put them. You need your glasses to find your glasses. This is a way that you can make a quick, emergency pair of glasses for yourself or someone else that needs them.
Any time you hear a sound, it is because something is vibrating. Place your fingers against your throat and hum. You will feel your throat vibrate. We usually hear sounds from vibrations that travel through the air, but solids can be much better at carrying vibrations.