Heart sounds

The heart sounds are the sound generated by the beating heart as the result of blood flow through it. This is also called a heartbeat.

In healthy adults, there are two normal heart sounds often described as a lub and a dub (or dup).
produced by the turbulent blood flow against the closed AV valves and semilunar valves .

The “lub” in the lub – dub.
is low pitch (25 – 45 Hz),
slightly prolonged (0.14 - 0.15 second).
This sound is primarily because of the closing of the mitral and tricuspid valves(AV valves).
It is normally loudest at the apex area.
S2 is the “dub” in the lub- dub.
high pitch (50 Hz).
is shorter (0.12 second).
The sounds are because of the closing of the Pulmonic and Aortic valves (end of systole ).

The interval between the aortic and pulmonary valve closure during deep inspiration is long enough for the second sound to be reduplicated (physiological splitting). The aortic component of S2 is well heard in the aortic area while pulmonic component of S2 is usually heard only in pulmonic area.

A soft (0.1 second),low pitched.
Due to rapid ventricular filling and due to vibration set up by inrush of blood.