LeviLabs: learning about sound through acoustic levitation

Sound waves are often studied as part of mechanical waves in the upper-secondary and undergraduate physics curricula. Acoustic levitation is an application of standing-wave phenomena, growing in popularity through the recent adoption of low-cost ultrasound transducers. Nevertheless, acoustic levitation has not yet been included in the standard phenomena investigated in undergraduate and upper-secondary physics courses. The objective of this Frontline is to introduce acoustic levitation in the classroom. This is done with LeviLab, a low-cost and easy-to-use experiment, accompanied by three hands-on procedures (LeviLabs): modifying the cavity length, visually representing standing waves with multiple levitated particles, and a tactile experience by moving a single particle between nodes. The first procedure yields the most accurate speed of sound measurements, while the second and third offer valuable qualitative insights into standing wave properties. This work demonstrates the educational potential of acoustic levitation to investigate sound waves. It aims to make the phenomenon accessible as a learning resource for upper-secondary and undergraduate physics laboratories by providing engaging hands-on experiences for qualitative and quantitative exploration.