Purpose: To demonstrate that sound will not be transmitted in a vacuum.

Bell jar, vacuum pump, buzzer, microphone, audio amplifier.

Since the vacuum pump makes considerable noise, it is best to make certain the apparatus is working and then start the vacuum pump to produce the desired vacuum inside the bell jar. After the container has been evacuated, close the stopcock to the bell jar and turn the pump off. With the buzzer, amplifier, and microphone on, slowly open the stopcock so that a little air will start to enter. With the air slowly coming in, the buzzer should continue to get louder and louder until the inside pressure is the same as atmospheric pressure.

References:

Manual: None