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. 2023 Apr 12;13(3):455–463. doi: 10.1007/s13534-023-00275-x

Fig. 4.

Fig. 4

Preprocessing of the raw PPG signal to remove noise. a Raw PPG signal with noise caused by small movements and muscle tremors. b Signal after removing baseline drift using discrete wavelet transform (DWT). c Signal after moving average filter to smooth the signal