Acoustic manipulation in air using a standing wave field

Using a standing wave field generated between a transducer and a reflector, it is possible to trap small objects at nodes of the sound pressure distribution in air. In order to trap and manipulate objects stably, the force should be strong enough and focused at a small region, In the present paper, a sound field was generated under a flat or concave reflector, and the sound field had been studied both by experimental measurement and numerical calculation. The sound pressure distribution of a standing wave field has been measured by a small microphone and calculated numerically using Rayleigh's formula. The calculated result agrees well with the experimental data. The sound pressure in the case of a concave reflector is higher and the region for high sound pressure is smaller compared to the case of a flat reflector.