Heart sounds measurement using PVDF film sensor and their comparison with RR intervals of ECG signals

Heart sounds are generated by the fluctuations of blood velocity and the vibrations of cardiac structure. The auscultation of heart sounds is one of the basic tools for patient diagnosis and provides a lot of information associated with cardiovascular systems. For converting mechanical sound waves into electronic signals, PVDF (polyvinylidene fluoride) film sensor was used as heart sounds measurement device. After suited filtering process, the first (S1) and the second (S2) heart sounds components were plainly distinguished and their peak timings were closely corresponded to reference heart sounds signals measured by microphone. Lastly, there was high correlation between S1 intervals (from PVDF signals) and RR intervals (from ECG signals). So it is expected that S1 intervals can replace RR intervals. In future application, these methods have possibilities for non-intrusive heart rate estimation.