Two-Dimensional Ultrasonic Air Temperature Tomography Based on Phase Shift Processing of Multifrequency Measurements

An iterative method of transmission tomography of air temperature heterogeneities based on ultrasonic sensing is proposed. The direct dependence of the speed of sound in air on temperature is considered. Air flow and related nonstationary effects are not considered. A change in the speed of sound affects the change in the phase shift of ultrasonic waves passing through the area under study. The reconstruction of the spatial distribution of heterogeneities is carried out by tomographic processing of phase differences of waves passing in forward and reverse directions. The phase differences between forward and reverse propagation waves in an a priori specified medium are considered. In the first iteration, a homogeneous environment is considered as an a priori given environment, and in the second iteration, the reconstructed heterogeneous environment obtained in the first iteration is considered. The results of numerical modeling and the results of experimental studies at frequencies from 38 to 43 kHz are presented. The possibility of reconstructing the distribution of temperature of air is shown.