A Review of Computer-Aided Heart Sound Detection Techniques
Table 1
The characteristics and significance of heart sounds.
Heart sound
Cause
Features
Significance
S1
Closure of the mitral (M1) and tricuspid (T1) valves, opening of the semilunar valve.
Frequency: 50–150 Hz
For the diagnosis of ventricular contractility and atrioventricular valve function, myocarditis, cardiomyopathy, myocardial infarction or heart failure disease.
Time: 50–100 ms
S2
Deceleration of blood flow in the aorta and pulmonary artery, closure of the semilunar valve, opening of the atrioventricular valve.
Frequency: 50–200 Hz
Relates to the functional state of arterial wall, high/low blood pressure, atherosclerosis, pulmonary heart disease, primary/pulmonary stenosis, left-to-right shunt congenital heart disease.
Time: 25–50 ms
S3
The blood flowing rapidly from the ventricle impacts the wall of the chamber from the atrium, causing sudden tension and vibration of the ventricular wall, chordae and papillary muscles.
Frequency: 25–70 Hz
Appears in some healthy young people.
Time: 120–150 ms
S4
Tension and vibration caused by atrioventricular valve and its related structures.
Frequency: <30 Hz
Belongs to pathological heart sounds, appears in some elderly populations and people with early coronary heart disease.
