An algorithm for calculation of the first and second heart sounds based on an oscillatory model with two degrees of freedom is proposed. The model takes into account elastic parameters of the aortic and pulmonary valves, blood flow in the nearby vessels, and their elastic oscillations. The force acting on the pulmonary valve during its closure was calculated on the basis of pressure differences in the right ventricle and pulmonary artery, which were determined from right heart catheterization data. The calculated heart sound profiles were compared with the measured phonocardiogram signals recorded during catheterization. A good correspondence of signals with optimal choice of valve and vascular parameters was shown. It was found out that the ratio of peaks, frequency and duration of heart tone signals are most sensitive to the value of pressure change rate during valve closure. It is shown that with the help of the developed model it is possible to predict the type of pressure profile in the right ventricle after drug administration for pulmonary hypertension. The results obtained using the algorithm can be used to gain a more detailed understanding of normal and abnormal heart tone generation in humans, and to develop new methods for diagnosing heart disease.
$^2$National Medical Research Centre of cardiology named after academician E.I. Chazov of Ministry of Health