The bell jar (named for its shape) and vacuum plate are supplied with a battery-operated electric bell. This pump plate and bell jar can be used to demonstrate the nature of sound waves by showing that sound does not exist in a vacuum. As air is pumped out of the jar the sound from the bell becomes fainter and fainter until it disappears. Includes bell jar, vacuum plate with valve, rubber seal, bell and instructions Bell may be removed for other vacuum experiments Tubing included Electric Vac Pump required - not included. 2 x AA Batteries required - not included.