Langevin Transducer Analysis and Acoustic Levitation

In this experiment we investigated the behavior of a 40W commercial, ultrasonic transducer. We observed a frequency response hysteresis near the resonant frequency of 28 kHz and determined that the resonant frequency depends on temperature and driving amplitude. We then used the transducer to create a resonant standing wave to levitate small objects including water drops. We show the non-linear acoustical theory to support the acoustic levitation force being produced by a nonzero time-average pressure. Using Schlieren optics we were able to observe pressure variations and measured relative pressures using a microphone. From the dynamical behavior of a levitated object, we were able to estimate the pressure amplitude of the standing wave