Bell Jar Experiment of Sound

bell jar

Sound is a mechanical wave which needs a medium to propagate. The medium can be air, liquid, or solid. Sound waves travel in the form of longitudinal waves. Longitudinal waves vibrate in the direction of propagation. However, sound waves require a medium to propagate. Let us try this  Bell Jar Experiment to experience this phenomenon.

Try it yourself

You need:

  1. An air tight glass bell jar
  2. A sound producing toy
  3. Vacuum pump
  4. Cork

What next?

Step 1: Connect the toy and the vacuum pump to airtight glass bell jar.

Step 2: Let the toy be in operation.

Step 3: Experience the sound and its intensity.

Step 4: Use the vacuum pump to pump out air from the jar.

You will notice that the sound fades as the air pressure falls within the jar. At the end the sound stops completely as all the air from jar gets pumped out to create vacuum inside.


Sound needs a medium to travel. Sound waves can propagate only through a medium of air, liquid, or solid.

If you enjoyed our Bell Jar Experiment, try other experiments that you can perform easily at home here.

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