Hand-pumped vacuum shade

MACHINE TRANSLATION (not authorised yet)

Economic version of classic help demonstrating that sound waves do not propagate in a vacuum. The set includes a transparent bell lamp shade (4-6V AC/DC power supply, flat battery or power supply (included)) placed on a rubberised base with a built-in hand pump enabling significant gas dilution inside the lamp shade and lowering the bell volume. The use of a hand pump makes the aid available at a price and, although it does not provide vacuum conditions, it presents the difference in volume.
KIT READY TO USE after purchase (no need to buy additional items).