An effective method on reducing measurement noise based on Hilbert-Huang transform

For non-stationary signal in ultrasonic inspection, an effective denoising method based on Hilbert-Huang transform (HHT) is presented and a few key questions using the HHT method are discussed. The overall scheme of HHT includes two parts which are empirical mode decomposition (EMD) algorithm and a sum of intrinsic mode functions (IMF). Through the EMD process, individual IMF can be found. The IMF coefficients are preceded in useful signal dominative layers using a soft threshold method and finally those IMF coefficients are reconstructed. The results show that the usage of HHT method is reasonable at removing the measurement noise than the wavelet transform.