The original Kundt’s experiment visualizes resonance modes inside a uniform tube with the both ends closed. The next video shows a 2-deminsinal Kundt’s experiment , visualizing resonance modes inside a uniform tube with one end closed and the other end open.
Please take a look at the narrow uniform-tube part of this setup. The left end of this uniform tube is connected widely spaced part, and it is considered as an open end. At the right end, on the other hand, a loudspeaker is connected and sinusoidal waves are input through it with a variable frequency. In this video, you can see cork dusts form ripples around the left end, because there is an antinode at this open end when the frequency matches the one for the first/fundamental resonance mode. Resonances occur due to multiple reflections at the both ends. It means that reflection occurs not only the closed end but also at the open end.
- Sakamoto, S., Ueno, K. and Tachibana, H. (2004). “Visualization of resonance phenomena for acoustic education,” Proc. ICA, III, 2311–2312.