Noninvasive acoustical analysis system of coronary heart disease

A noninvasive heart sound detecting and analyzing system for coronary heart disease (CHD) was developed. As the signal-to-noise ratio is very low, an electret condenser transducer was introduced and transducer soundproof cover was designed. The sensitive system collected heart sound from the subsonic area to 1200 Hz, including the turbulent sound produced by blood flow and vibration of myocardium,and artery. Wavelet transform method and autoregressive (AR) modeling method were used to analyze the signals in the time-frequency domain. The maximum, energy ratio and spectrum position of heart sounds, as characteristic parameters in the higher frequency band, as well as in the lower frequency band (subsonic area) were studied. The signals on both diastole and systole periods were considered. The performance of the system has been evaluated in 67 samples that contain 534 cardiac cycles including normal and CHD subjects. The result showed that this system was effective to detect heart sounds produced by coronary heart diseases. The correct classification was about 78% for normal subjects and 83% for CHD patients