Differentiate Between Lub And Dup Sound

The sound lub-dup in a cardiac cycle is the period between the end of one heartbeat to the end of the next heartbeat is called a cardiac cycle. The cardiac cycle is formed of three phases:

  • Atrial systole
  • Ventricular systole
  • Joint diastole

The sounds of lub-dup can be heard during a heartbeat by placing a stethoscope on the chest wall above the heart.

Lub And Dup Sound – Differences.



It is the first sound heard during a heartbeat.

It is the second sound heard during a heartbeat.

The lub corresponds with the ventricular systole.

The dub corresponds with atrial systole.

The lub sound is fairly loud due to the closure of the atrioventricular valves.

The dub sound is softer due to the closure of the aortic and pulmonary valves.

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