Correlation between instantaneous pressure gradient curve and envelope of the heart sound

The curve of instantaneous (at intervals of 0.02 sec) pressure gradients between the communicating chambers of the heart is the envelope of the heart sound. This indicates that it is proportional to the curve of instantaneous blood flow velocities in this part of the system. Hence it follows that the higher the pressure gradient, the higher the velocity of the blood flow and the greater the amplitude of oscillations on the phonocardiogram.