Enhancement of convergence efficiency for airborne ultrasonic self-bending beam with phase-modulating reflector

Abstract

Abstract Acoustic self-bending beams for airborne ultrasound are highly expected to expand the capabilities of existing acoustic applications. Our previous study has implemented amplitude control based on the Airy function to achieve an ultrasonic self-bending beam in air. However, the amplitude control lacks sound pressure convergence into the main lobe. To improve the convergence, we propose using a reflector to achieve phase modulation. In this study, we used the Airy function and developed the reflector that incorporates different heights to control spatial phase distribution. Using the proposed reflector demonstrated a self-bending beam for an airborne ultrasound experimentally. In addition, compared to the amplitude modulation, the phase modulation using the proposed reflector improved convergence efficiency of sound pressure level by more than 6 dB at distances of 0.7 m and 1.0 m from the emitter.