Lub and dub are the normal heart sounds (noise) created by the heart. The heart sounds are produced due to the turbulence of blood flow by the valves.
Lub - It is the first heart sound (S1), is heard due to turbulence caused by bicuspid/mitral valve and tricuspid valve during contraction of ventricles.
Dub – It is the second heart sound (S2), is heard due turbulence aortic and pulmonic valves during ventricular relaxation.
