What's the science?
Sounds are made by vibrating objects. The vibrations spread out within a solid, liquid or gas, and we hear the sound when the vibrations reach our ears. Your vibrating coat hanger creates sound waves in the air, but it doesn’t have a large surface area, so it doesn’t disturb much air – and the vibrations spread out in all directions. That’s why the sound is very hard to hear. But the vibrations will also pass up the strings – and, when your fingers are in your ears, into the skin and bones of the ear. Much less sound is lost, so you hear the sound very clearly.
Science in our world
Stethoscopes help us to hear sounds from inside the human body. Just like the strings in the activity, the stethoscope tubes prevent the sound from spreading out in all directions, and channel it to the doctor’s ears. The first stethoscope was made in 1819, from paper rolled into a tube. Why not try making your own? See if you can hear a friend’s breathing or even their heartbeat.
Did you know?
Most humans can hear sounds produced by objects vibrating up to around 20,000 times per second.
How does the sound change when you:
• Use longer or shorter string?
• Use wool or ribbon in place of the string?
• Replace the metal coat hanger with a different material?