Quantitative calibration of sound pressure in ultrasonic standing waves using the Schlieren method

We investigated the use of the Schlieren method to calibrate the sound pressure in an ultrasonic standing-wave field. Specifically, we derived an equation to calculate the light intensity of the diffraction fringe induced by the standing-wave field. The results indicated that the sound pressure in the standing-wave field relates to the light intensity of the diffraction fringe. Simulations and experiments were conducted to verify the theoretical calculation. We demonstrated that the ratio of the light intensity of different diffraction orders relates to the sound pressure amplitude, allowing the pressure amplitude to be calibrated with the Schlieren method. Therefore, this work presents a non-intrusive calibration method that is particularly suitable for calibrating high-frequency ultrasonic standing-wave fields.