Ultrasonic reflectometry in air: errors of sample positioning

The reflection coefficient of ultrasonic waves propagating in air and interacting with a plane surface of a solid is considered. The simulation of dependence of the reflection coefficient on errors of sample positioning is performed using a finite beam model along with an angular spectrum method, and next the results are validated experimentally. The simulations show that for the considered range of geometrical parameters, the role of the wave divergence for the reflection coefficient in air is insignificant. The important consequences of errors of the sample positioning are that the shift of the sample influences mostly the phase, while the errors of inclination of the sample mainly affect the magnitude of the reflection coefficient. The experiments confirm simulation results pointing out the necessity of high precision of measurements for ultrasonic reflectometry in air. The results can be used for assessment of precision, calibration, and reduction of errors in applications of the reflectometry tests.