Time frequency analysis of impact-echo signals: Numerical modeling and experimental validation

Since the middle of the 1980s, the impact-echo method, based on an analysis of the transient response of structures in the frequency domain, has been applied successfully to several kinds of fault search techniques for concre te. The objective of this paper is to present a signal processing technique that can improve interpretation of impact-echo signals either when the cur rent method fails or when the diagnosis is not straight forward. This new t ime frequency analysis of the signal is presented both through the analysis of numerical signals calculated using the finite element method, and throu gh the analysis of experimental signals recorded on a concrete test slab. T he paper also reviews, by means of a comprehensive and efficient signal pro cessing model, the main set of parameters influencing the method.