Examination of Noncontact Excitation of Acrylic Board Using High-Intensity Aerial Ultrasonic Waves Having Finite Amplitudes

Abstract

We examined the possibility of exciting an object in a noncontact manner using high-intensity aerial ultrasonic waves. We performed experiments using various acrylic samples having different thicknesses and high-intensity aerial ultrasonic waves (at the frequency of 20 kHz) which were converged into a circular area of about 1 cm in diameter. The results indicated that the vibration displacements occurring in the samples were proportional to the sound pressure of the ultrasonic waves radiated onto the samples. In addition, the distribution of vibration displacements corresponded to the distribution of sound pressures formed by the ultrasonic waves radiated on the surfaces of the samples. The radiated ultrasonic waves used for these experiments had finite amplitudes so that they contained harmonic components at frequencies that were integral multiples higher than the fundamental frequency. Therefore, it was concluded that the samples irradiated with the ultrasonic waves vibrated not only at the fundamental frequency (20 kHz), but also at the frequencies of 40, 60, 80, and 100 kHz at the same time.