Air column resonance in a horizontal glass tube is shown by adding cork dust to the tube and driving the air column with a speaker at one end of the tube. Accumulation of cork dust shows nodes (displayed on overhead projector). Tube length may be varied with a sliding stop at the far end.
1) Robert A. Carman, "Kundt Tube Dust Striations." American Journal of Physics 23:8, 505 (1955).