Solution: Every cardiac cycle produces two sounds: lub and dub, which are produced by a heartbeat. The sound is produced in a specific order, in time with each heartbeat. The initial sound is a low-pitched ‘Lub.’ It occurs when both the bicuspid and tricuspid valves collapse. When the semilunar valve closes, the second sound is called ‘dub.’ This is a high-pitched sound. Both of these sounds are important in the identification of any heart condition.