A new method for eliminating speckle noise from Laser Doppler Vibrometer signals

Abstract

As the durability and stability of structures in operation are required, effective technologies are necessary to monitor the structural health. Laser Doppler vibrometer (LDV) is a non-contact and non-destructive vibration detector suitable for acquire broadband signals remotely and continuously. The significant signal issue is speckle noise mainly by LDV scanning from moving platforms (LDVom). This paper presents a novel approach based on ensemble empirical mode decomposition for eliminating speckle noise. The instantaneous frequency in intrinsic mode functions (IMFs) corresponds to the instantaneous vibration that is acquired by LDVom, and the signal is continuous in a sole IMF. In numerical simulations, the EEMD-based approach can effectively reveal the true vibration despite intensive noise. The correlation coefficient remains over 0.9 when the initial signal-to-noise ratio decreases to -15 db. In experiments, the 500 Hz vibration is almost revealed by EEMD regardless of the noise intensity and the vibration strength. Therefore, our approach is applicable in eliminating speckle noise.