A denoising algorithm for an electromagnetic acoustic transducer (EMAT) signal by envelope regulation

To reduce the noise in the inspection data of an electromagnetic acoustic transducer (EMAT), a denoising method using an envelope regulation technique is proposed. A cubic polynomial interpolation curve fitting method is used to obtain the envelope of the original signal. The upper envelope and the lower envelope are used separately to modify the original signal according to a chosen denoising threshold. The upper and lower modified signals are averaged to get the final result. The algorithm can suppress small-amplitude high-frequency noises mixed in the signal, without damaging the main feature of the signal. The algorithm is tested by an experiment with EMAT surface wave data. The result shows that the denoising algorithm based on envelope regulation can effectively eliminate the clutter and burrs in the inspection data, and improve the signal-to-noise ratio.