I. Introduction
Many technologies that use aerial ultrasonic waves have been developed, for applications including biological analysis, and velocity and position sensors. Aerial ultrasonic waves are suitable for noncontact techniques and shape directionality. High-intensity aerial ultrasonic waves can be used for noncontact applications [1], [2] such as transport of small objects, atomization of liquids [3], [4], removal of adhered fine particles [5], and the removal of liquids in pores [6]–[9]. These applications require the target to be irradiated directly with aerial ultrasonic waves. However, the range of suitable applications of aerial ultrasonic waves would be expanded if targets could be irradiated indirectly. One possible application is stirring reagents [10]–[13] in the field of chemistry. A noncontact method for stirring liquids by irradiation with ultrasonic waves could overcome various problems.