Acoustic Standing-Wave Field for Manipulation in Air

A noncontact manipulation technique is necessary in micromachine technology. Using a standing-wave field generated between a transducer and a reflector, it is possible to trap particles at nodes of a sound pressure field. In the present paper, a sound field has been studied by both experimental measurement and numerical calculation. The sound pressure distribution of a standing-wave field was measured using a small microphone and calculated numerically using Rayleigh's formula. Although Rayleigh's formula is usually used to calculate direct sound pressure from a sound source, it has been shown that the sound pressure of the standing-wave field can be calculated by Rayleigh's formula by adding multiply reflected waves.