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. 2017 May 10;17(5):1082. doi: 10.3390/s17051082

Figure 4.

Figure 4

Preprocessing audible sound of a weld bead, (a) spectral signal derived from FFT; (b) spectral signal after average downsampling. Burn through audio signal (in blue), shrinkage cavity audio signal (in green) and desirable weld audio signal (in red).