Novel phonocardiography system for heartbeat detection from various locations

Figures

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  Figure 1. General scheme of direct PCG segmentation2.

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  Figure 2. Block diagram of the DAQ system.

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  Figure 3. 3D printed extension connected to the microphone.

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  Figure 4. The selected auscultation points for PCG recording (P1–P7): red—traditional auscultation areas, blue—additional areas, green—0reference points.

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  Figure 5. PCG preprocessing steps (volunteer #2, position P3).

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  Figure 6. Envelope of the PCG signal (gray curve) with detected peaks (red) above the \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$Th_{1}$$\end{document}Th1 threshold (blue dashed line). The \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$Th_{2}$$\end{document}Th2 threshold (black dashed line) is intended to further peaks classification (volunteer #2, position P3).

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  Figure 7. Intervals between even (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$T_{e;n}$$\end{document}Te;n) and odd (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$T_{o;n}$$\end{document}To;n) peaks. Correctly detected intervals (which correspond to the HR) are marked in green. Intervals marked in red are detected incorrectly due to non-detected peak (marked with a purple circle); volunteer #4, position P3.

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  Figure 8. Interval-based peak assignment. S1 before systole (S, red), S2 before diastole (D, blue) and non-classified peaks before longer intervals and below the threshold \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$Th_{2}$$\end{document}Th2 (purple); volunteer #4, position P3.

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  Figure 9. Conditions for peak removal and assignment.

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  Figure 10. Intervals for evaluation of HS detection quality; volunteer #4, position P3.

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  Figure 11. SE and PPV of HS detection in hybrid boxplots.

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  Figure 12. Faulty detection due to low S2 amplitude—reference ECG (gray curve), PCG envelope (blue curve) with detected peaks (red) and expected positions of S2 (black circles); volunteer #25, position P5.