heart sound

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 Heart sounds are the sounds produced by mechanical activities of heart during each cardiac cycle.

Heart sounds are heard by placing the ear over the chest or by using a stethoscope or microphone.

Four heart sounds are produced during each cardiac cycle:

FIRST HEART SOUND

 • First heart sound is produced during isometric contraction period and earlier part of ejection period

 • This sound is produced due to the closure of atrioventricular valves.

 • The sound is long ,soft ,low pitched and Resembles the word LUUB

 • The duration of this sound is 0.10 to 0.17 second.

 • Its frequency is 25 to 45 cycles/second.

SECOND HEART SOUND

 • Second heart sound is produced at the end of protodiastolic period.

 • Second heart sound is produced due to the closure of the semilunar valves

 • It resembles the spoken word ‘DUBB’ (or DUP).

 • Duration of second heart sound is 0.10 to 0.14 second.

 • frequency is 50 cycles/second

THIRD HEART SOUND

 • It is a low-pitched sound that is produced during rapid filling period of the cardiac cycle.

 • It is inaudible by stethoscope

 • it can be heard only by using microphone.

 • is produced by the rushing of blood into ventricles .

 • Duration of this sound is 0.07 to 0.10 second.

 • Its frequency is 1 to 6 cycles/second.

FOURTH HEART SOUND

 • the fourth heart sound is an inaudible sound

 • Fourth heart sound is produced by contraction of atrial musculature

 • Duration of this sound is 0.02 to 0.04 second.

 • Its frequency is 1 to 4 cycles/second.


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