Baseline-free damage localization methods in structural health monitoring are of interest. We conducted a pump-probe experiment on metal plate. PZT patch generates a probe wave at 20 kHz, a continuous pump of 1 Hz is produced by a shaker. The aim was localization of a steel ball pressed against metal plate. We received reverberated signals with PZT patches. These reverberations are affected by a current coordinate of the ball i.e. by a local change in geometry. We subtract signals recorded at different times (corresponding to different loading states) and apply the backpropagation algorithm that locates the origin of the modulation.