An introduction to wavelet transforms: a tutorial approach

Abstract

Non-destructive testing (NDT) and condition monitoring techniques are among the most rapidly developing engineering disciplines. In the past decade methods have been sought to enable real-time or on-line analysis of degradation in structures ( 1 - 3 ) . Methods developed in the 1980s based on modal analysis ( 4 ) have resurfaced, partly due to new developments in signal processing. Many of the on-line NDT techniques currently under research utilise wavelet transforms ( 5 - 9 ) to decompose spatial signals into the time/frequency domain. The aim of this paper therefore, is to provide a friendly tutorial to the two most commonly used forms of the wavelet transform. It is hoped that this article will provide interested readers with sufficient knowledge of the subject to allow productive usage of the various software packages offering wavelet technologies. Being aware of the building knowledge provided both by literature and the internet, a list of useful references and world-wide-web links has been provided at the end of the paper.