 August Kundt

August Kundt made standing wave patterns of sound waves visible through the dust patterns in Kundt's tube. Neighboring repeat marks in the ideal pattern are separated by half a wavelength, so a measured spacing $d$ and known frequency $f$ give speed of sound $c=2fd$. The tube turns an oscillation too rapid to follow directly into a spatial ruler. Comparing resonance conditions in a solid rod and a gas also connects the method with measurements of sound propagation in different materials.^[ref]

A physicist whose appointments took him from Zürich in 1868 through Würzburg and Strasbourg to the Berlin chair of experimental physics in 1888.^[ref]

August Kundt is typically associated with the "Kundt's tube," which is a scientific apparatus used in acoustics to demonstrate standing waves in a gas or liquid medium. The device consists of a tube that can be partially filled with a medium, and a loudspeaker or other sound source that generates sound waves. By adjusting the frequency of the sound, one can visualize standing waves formed along the length of the tube, which leads to the observation of nodes and antinodes.