I Hear a Hangar
Objective: To observe (with your ears) the difference in sound transmission in air
and in a solid object (like your head).
Materials:
Metal Hangar
Two pieces of string (about 18 inches or so—longer is better than shorter)
Procedure:
1. Tie the strings to each “corner” of the hanger, as shown.
2. Carefully wind each of the strings tied to the hangar around each of your
index fingers. The hangar should be hanging from your fingers so that you
can swing the hanger into a chair or table (If you’re standing with elbows
bent at 90 degrees, the hangar should be hanging at waist or knee level).
3. Gently swing the hangar into a chair or table, and listen to the sound it
makes.
4. Next, put your index fingers in your ears, and repeat step 3. Does it sound
different?
What’s Going On?
Sound is a form of mechanical energy, and travels in waves. Waves of sound,
however, must travel through something in order to be heard (sound cannot travel through a vacuum). Sound travels
much better through a solid (like your head) then it does through a gas (like the
air).
Think and Talk About This:
Do you think changing what the hangar is made of will change the result? Try it
with a plastic or wooden hangar.
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