3B30.30- Bell in a Jar

Description: This demonstration shows that sound cannot travel in a vacuum .


  • Vacuum Pump
  • Bell/Buzzer
  • Bell Jar
  • Power Source


  1. Connect the bell/buzzer to a power source and turn it on.
  2. Place bell/buzzer in bell jar and seal it.
  3. Connect vacuum to bell jar and remove air.

Concept: As the air is removed from the bell jar, the sound of the bell/buzzer starts to fade. When most of the air is out of the jar, the sound can barely be heard. This demonstrates how sound waves cannot travel due to the lack of a medium.


  1. If using a bell, do not allow the bell to come in contact with the side of the bell jar. It will cause the vibrations of the jar to be heard.
  2. For best results, the buzzer will yield the best demonstration.
  3. If using clamps to connect the bell/buzzer to the power source, make sure they don’t touch.