Question

The initial vibrations occur when the first contraction of the ventricle move blood towards the atria, closing the av-valves.

Answer 1

Heart sounds are discrete bursts of auditory vibrations of varying intensity (loudness), frequency (pitch), quality, and duration. The first heart sound (S1) is composed of several high-frequency components; only the first two are normally audible. These two sets of audible vibrations are temporally related to closure of the mitral and tricuspid valves. The first heart sound coincides with contraction of the ventricles, thus identifying the onset of ventricular systole and the end of mechanical diastole.