Without air or matter, sound waves cannot travel and therefore cannot be heard. This bell jar effectively demonstrates this concept using a battery–operated buzzer housed inside an acrylic tube. When the buzzer is placed beneath the jar and a vacuum seal is created in the chamber, students will observe a total absence of sound. Once air is returned to the chamber, the sound of the buzzer can be heard once more. Activity requires a vacuum pump, not included.

Height 14cm, 10 cm Ø