Book 14, Question 16
Why Does a Bottle Hum When You Blow Across the Top?
A bottle hums when you blow across the top because the air inside starts to vibrate! Your breath makes the air in the bottle bounce back and forth. That steady bounce is the hum you hear.
More fun facts
- Blowing across a bottle's opening makes the air inside vibrate.
- Your breath hitting the edge of the opening sets up pressure waves in the bottle.
- The air inside vibrates quickly and evenly, which makes a steady tone.
- A half full bottle sounds different from an empty one.
- You can play music with bottles filled to different levels.
Sources: National Geographic Kids, Smithsonian, Scientific American
Questions kids ask
Do full and empty bottles sound the same?
No. A half full bottle makes a different sound than an empty one.