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A heart beat generates two sounds – lub and dub, produced in every cardiac cycle. The sound is produced in a sequence, in-sync with every heartbeat. ‘Lub’ is the first sound and is low pitched. It is caused when the bicuspid valve and the tricuspid valve closes. ‘Dub’ is the second sound which arises when the semi-lunar valve closes. This sound is high- pitched. Both the sounds are significant in the diagnosis of any disorder of the heart.