Consideration of sample dimension for ultrasonic levitation

To study ultrasonic levitation, a high-intensity ultrasound field was generated in air by a new type of sound source using a stepped circular vibrating plate, and the sound pressure level was obtained up to 168 dB at a frequency of 20 kHz. This sound source was equipped with a reflecting plate. It was set in a 1-G environment, and the frequency could be changed by the different plates used. Several shapes of samples were inserted in the sound field, and the sample dimension was varied. As a result, the samples were levitated at the sound pressure nodes and the minimum threshold of sound pressure required for levitating the samples was found to be proportional to sample density, and was also inversely proportional to the ultrasound frequency used. The sample dimension was found to influence the sound pressure