Thaylen vacuum tube

A glass tube about a foot in diameter and several feet long, capped with thick metal screw-on chambers at each end, from the Royal Institute of Barometric Studies in Thaylenah. A fabrial pump evacuates the side chambers so the central glass can carry no sound. Navani uses it to let Voidlight drift across a soundless gap and 'hear' an anti-tone the first time it touches matter — the trick that produces anti-Voidlight. SA:RoW:Ch 97