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Sound

The normal audible heart sounds are produced by valves closing, akin to a door slamming shut in the wind

Turbulent blood flow can also cause sound, this turbulent flow can be caused by a damaged valve and the sound is called a murmur

There are four normal heart sounds, named S1, S2, S3 and S4 respectively

S1 and S2 are the only two usually heard, the classic Lub-dub of the heart

Diagram of S1 S2 S3 and S4 heart sounds

The above diagram shows the heart sounds as they would be heard in a perfect environment, as you can see S1 and S2 have two components to them

So what is happening to the heart when these sounds are occurring?

S1

This is the closure of the Mitral and Tricuspid valves

S2

This is the closure of the Aortic and Pulmonic valves

S3 and S4

These, when heard, are both filling sounds of the ventricles.

Diagram of heart sounds showing systole and diastole

In systole the ventricles are contracting and the resultant increase in pressure closes the mitral and tricuspid valves causing S1 (or lub-!)

At the end of systole the pressure in the ventricles drop as they start to relax and as blood (at high pressure) in the pulmonary artery and aorta tries to rush in they close the aortic and pulmonic valves, causing S2 (-dub)

Ok, so this is the first sound sample and is of a normal heart sound, notice how the sound is clean, clear and the sounds are relatively short.

**NOTE do not listen with small laptop speakers as they do not project enough bass, use headphones or reasonable speakers! **