Flow across valves are silent. Valves open silently. Valves make sound when they slam shut. Intensity depends on pressure with it slams shut.

• S₁ is produced by closure of mitral and tricuspid valves.
  • This occurs right after QRS in EKG.
• S₂ is produced by closure of aortic and pulmonary valves.
  • Pulmonary valve closes 60 msecs after aortic valve.
  • Aortic and pulmonary valves close after isometric relaxation period.
  • Pulmonary component is softer than aortic component.
• S₃ is due to rapid filling of Ventricles from atrium during diastole.
  • S3 may be normal in children and during Pregnancy.
  • S3 may be present in CHF.
• S₄ is due to atrial contraction.
  • S₄ is always abnormal and is due to noncompliant Ventricle.