The Heart Sounds

Four Heart sounds - all poduced either by closure of valves, vibrations or turbulence
 
First Heart Sound
  - Caused by sudden closure of the A-V Valves
  - Low pitched, 0.12 sec duration
  - Systolic
   
Second Heart Sound
  - Caused by sudden closure of Aortic and Pulmonary Valves
  - Higher Pitch and Shorter duration - 0.08 sec duration
  - Diastolic
Third Heart Sound
  - Vibrations in ventricular wall due to rapid filling with blood (Usually not heard)
  - Diastolic
Fourth Heart Sound
  - Auricular contraction and rush of blood into ventricle (Normally never heard)
  - End-Diastolic