Acoustic field measurement by midair scanning of an acoustically levitated microphone

Acoustic levitation is widely utilized to grasp objects in air that are sufficiently smaller than the wavelength. Recent development of phase engineering technique of airborne ultrasound transducers (airborne ultrasound phased arrays) has realized rotation and translation of levitated objects in an electronic manner. Based on this technological progress, this paper focuses on direct measurement of acoustic fields in a space through aerial manipulation of a small and lightweight levitation sensor system that we call a wired sensor unit. Our method is free from inconveniences with conventional methods such as robotic-arm-based sensor scanning that they can be dangerous when operated around human or that they lack in the flexibility of the operating range determined in advance. In this paper, the principle of acoustic levitation sensing is verified through an experimental demonstration of acoustic field measurement in a table-top workspace.