A Combined Denoising Method for Microseismic Signals from Coal Seam Hydraulic Fracturing: Multithreshold Wavelet Packet Transform and Improved Hilbert-Huang Transform

<div>Time-frequency comparison of the MWPT-IHHT and three commonly used denoising methods. (a) Original synthetic signal. (b) HHT. (c) WT. (d) WPT. (e) MWPT-IHHT.</div>

Shock and Vibration

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Figure 8

Figure 8: A Combined Denoising Method for Microseismic Signals from Coal Seam Hydraulic Fracturing: Multithreshold Wavelet Packet Transform and Improved Hilbert-Huang Transform 

Figure 8 | A Combined Denoising Method for Microseismic Signals from Coal Seam Hydraulic Fracturing: Multithreshold Wavelet Packet Transform and Improved Hilbert-Huang Transform 