STFT-Based Comparative Studies of Heart Sound Signals

The paper is focused on analyzing 20 heart sound samples, including patients with coronary disease and healthy persons. Short Time Flourier Transform (STFT) is adopted for the analysis, since Flourier Transform (FT) has its limitations as a tool in analyzing heart sound signals which as biological signals are weak and nonstable. The study demonstrates that the heart sounds of patients with coronary disease, including those with atrial septal defects, exhibit markedly different characteristics from those of healthy persons. Specifically, the first heart sound (SI) is closely followed by a systolic murmur of high frequency; a persistent splitting of the second heart sound (S2) is observed, which is accompanied by a diastolic murmur. It is therefore concluded that the frequency changes and structure of cardiac sounds are mainly related to the health of the heart and basically free from the influences of individual differences.