This sound is produced during the closure of the semilunar valves.
lubb
dupp
lubb dupp
lubb duppshhh
B: The second heart sound can be represented by dupp. It occurs at the beginning of ventricular diastole and results from the closure of the semilunar valves.
A: The first heart sound can be represented by the syllable lubb. It occurs at the beginning of ventricular systole and results from closure of the AV valves.