Jackson, David P., and Ming-Hua Chang. Acoustic Levitation and the Acoustic Radiation Force. American Journal of Physics 89, no. 4 (2021): 383-392. https://aapt.scitation.org/doi/full/10.1119/10.0002764

For more information on the published version and to access the video portion of the Abstract, visit AAPT's Website. Acoustic Levitation and the Acoustic Radiation Force was the featured article on the cover of the April issue of American Journal of Physics (Volume 89, No. 4, April 2021).

We investigate acoustic levitation in a vertical standing wave in an attempt to understand the basic physical mechanism responsible for this phenomenon. We find that a description in terms of a simple pressure force leads to the prediction of stable equilibria that occur slightly below the anti-nodes of the standing pressure wave. We then demonstrate that such a prediction is at odds with experimental data, which show that levitating particles come to rest slightly below the nodes of the standing pressure wave. Finally, we outline a theoretical approach based on fluid dynamics that correctly predicts the locations of the levitating particles, which leads to a simple qualitative description for this fascinating phenomenon.

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