How can acoustic resonance reduce the average velocity in a falling body?

in this article, a simple experiment is described to overcome the misconception that acoustic pressure and levitation effects are difficult to observe in school laboratories. analysis of the free fall velocity of a toy parachute inside a vertical tube, driven by sound in a range of frequencies aromid the resonant condition, exhibits the resonance frequency, the node pressure zones, and the optimal conditions to obtain acoustical levitation of a light body.