Acoustic emission signals are high frequency stress waves that are generated by rapid release of energy due to an initiation/growth of cracks, material dislocations etc. Sources of noise are present in applications where the AE testing environment is disturbed by mechanical vibrations and other background noise. Both AE signal and noise are high frequency signals and digital filters are not effective to extract the AE signal from the observed continuous signal. Wavelet packets can be used more

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... fficiently to denoise the signal and retrieve the signal of any desired frequency range. From the denoised signal AE event can be extracted by envelope detection and correlation analysis. Since wavelet packets can give better time-frequency resolution than other transforms, it is more suitable for locating defects also which is a major application of AE testing.