Quick Answer: The Vacuum Bell with Buzzer shows that sound needs a material medium to travel: an electric buzzer sounds inside a bell jar, and the sound fades as a vacuum pump removes the air. The set comprises a bell jar, buzzer unit, base plate, electrical connection and vacuum outlet.
Last updated: October 2026
Key Features
Electric buzzer placed inside a transparent bell jar
Base plate with vacuum outlet for connection to a pump
Sound weakens audibly as air is pumped out
Works with a vacuum pump and rubber vacuum tubing
Technical Specifications
Specification
Value
Components
Bell jar, buzzer unit, base plate, electrical connection, vacuum outlet
Application
Demonstration of sound propagation in air and vacuum
Compatible with
Vacuum pump and rubber vacuum tubing
Design
Transparent chamber for easy observation
About This Product
The apparatus is used in lessons on sound waves to show the role of air as the medium that carries sound. The buzzer is first heard clearly in normal air, then grows fainter as the pump evacuates the jar, which makes the link between air and sound easy for a class to observe. Educational Instrument can dispatch the Vacuum bell with buzzer to laboratories in Bahamas, Vietnam, Latvia, United Kingdom, Mozambique and Estonia.
Frequently Asked Questions
Why does the buzzer become quieter as air is removed?
Sound waves need a material medium such as air. As the pump removes air from the bell jar, less air is left to carry the sound.
