Kundt's tube
![Drawing from Kundt's original 1866 paper in Annalen der Physik, showing the Kundt's tube apparatus (fig.6 & 7, top) and the powder patterns created by it (fig.1, 2, 3, 4).](/Images/godic/202501/22/Kundt_tube1313.png")
![A modern version of the Kundt's tube experiment, used in a South American university physics class. Instead of a transparent tube with powder in it to reveal the nodes, this uses microphones mounted in the tube. The piston (right center) is moved back and forth. When the microphone's position is at the antinodes of the wave the sound pressure goes to zero. The sound power from the microphones is recorded on the chart recorder (center rear).](/Images/godic/202501/22/Tubo_de_Kundt1313.jpg")
Kundt's tube is an experimental acoustical apparatus invented in 1866 by German physicist August Kundt for the measurement of the speed of sound in a gas or a solid rod. It is used today only for demonstrating standing waves and acoustical forces.