Theoretical and practical aspects of applying time reversal of elastic waves to localize a source of oscillations or a defect are considered in problems of active ultrasonic monitoring of thin-walled metal structures. Backward reradiation of a time-reversed signal is implemented using a computer model based on a semianalytical integral approach. The proposed algorithm is verified experimentally on aluminum samples excited by piezoelectric wafer active sensors. The results corroborate the possibility of reliably determining of the position and size of the load application region and a local inhomogeneity with a relatively small number of signal measurement points on the sample surface.