Acoustic Particle-Field Interactions: Measurements, Visualizations, and Awareness

Abstract

Scientific investigations are fundamental to physics and physics education. Central to these are experiments that enhance learning, facilitate the visualisation of complex phenomena, and enable students to test and refine their models. Within the classroom setting, experiments serve both as demonstrations and as practical laboratory activities. In this project, aspects of acoustic particle–field interactions are investigated by developing experimental setups and measurement methods appropriate for both educational and scientific contexts. In the first paper, a novel experimental method was developed to determine the volume of microlitre-sized droplets in acoustic fields by utilising simulations of the acoustic field to guide the adjustment of the cavity length. A rapid and self-calibrating procedure was established for accurate volume measurement in horizontally oriented uniaxial levitators. This approach advances the precision and efficiency of droplet volume determination in levitation-based experiments. In Paper II, an experimental apparatus called LeviLab was developed for educational use, enabling students to visualise and investigate the properties of acoustic standing waves through the acoustic levitation of polystyrene particles. Accompanying LeviLab, three experimental methods were designed for students to determine the wavelength of sound and to calculate the speed of sound, each of which was evaluated for measurement accuracy. This work contributes to making acoustic levitation accessible for physics instruction in schools. In Paper III, the experimental setup LeviLab was employed to experimentally determine absolute zero through an acoustic levitation experiment. Two approximate models describing the relationship between temperature and the speed of sound were compared and analysed. This experiment was proposed as a practical laboratory activity for upper-secondary school physics, aiming to enhance students’ understanding of thermodynamics and sound properties through hands-on investigation. In Paper IV, acoustic levitation was employed, to the authors’ knowledge, for the first time by students working alongside generative AI as a laboratory partner. This study investigated how students engaged with generative AI to comprehend the experimental setup, LeviLab, and the accompanying laboratory manual, enabling them to conduct measurements and reason about acoustically levitated particles. The findings highlight the importance of educating students on the capabilities and limitations of AI tools to ensure their effective and responsible use within physics education laboratories. Finally, in Paper V, acoustic levitation was incorporated, to the authors’ knowledge, for the first time by students working in an ecological (authentic) classroom setting. The study examined the qualitatively different ways in which students experienced a particle suspended mid-air within a standing wave acoustic levitator. From the laboratory manual developed in Paper IV as a pilot, an experimental learning activity was designed around the LeviLab experiment to allow students to explore various aspects of the phenomenon. Semi-structured post-interviews were conducted, and a phenomenographic approach was employed to organise student conceptions into a hierarchically ordered outcome space, identifying critical aspects that differentiated the categories. This work paves the way for both future research and physics educators to utilise acoustic levitation experiments as a valuable learning resource.