Fig. 4: Construction of the phonocardiogram (PCG) and seismocardiogram (SCG) signal from recordings of heart sound and heart vibrations.

The workflows depicted in a and b correspond to the PCG and SCG signal respectively. After the data are recorded, they are typically downsampled. Subsequently, a band-pass filter is applied. S1 and S2 are the two main heart sounds, representing the closure of the mitral and tricuspid valves, and the closure of the aortic and pulmonary valves, respectively.