An ideal solution to the common physics experiment demonstrating that sound will not travel in a vacuum. Transparent jar and pump, both having unbreakable ABS body. Jar provides a robust chamber capable of with standing full vacuum for basic experiments with low pressure. A manual exhaustion piston pump integrated into base plate and  a rubber gasket ring on the pump base ensures air tight seal with the jar. Fitted with vacuum release valve  and vacuum gauge for measuring pressure. complete self-contained apparatus. Inside bell jar electric bell that requires a suitable DC power supply (3–6V). Connection to a power supply is made via two 4mm terminals on that protrude at  the  base. Bell jar dimensions 200 mm. height  x 250 mm diameter. To demonstrate  that sound waves does not travel in a vacuum.