How to Study Heart Sounds


Heart sounds are studied by three methods:

1. By using stethoscope

2. By using microphone

3. By using phonocardiogram.

How to Study Heart Sounds


First and second heart sounds are heard on the auscultation areas, by using the stethoscope. The chest

piece of the stethoscope is placed over four areas on the chest, which are called auscultation areas.

Auscultation Areas

i. Mitral area (Bicuspid area)

Mitral area is in the left 5th intercostal space, about 10 cm away from the midline (midclavicular line). Sound produced by the closure of mitral valve (first heart) sound) is transmitted well into this area. It is also called apex beat area because apex beat is felt in this area.

Apex beat

Apex beat is the thrust of the apex of ventricles, against the chest wall during systole.

ii. Tricuspid area

Tricuspid area is on the xiphoid process. Sound produced by the closure of tricuspid valve (first heart

sound) is transmitted well into this area.

iii. Pulmonary area

Pulmonary area is on the left 2nd intercostal space, close to sternum. Sound produced by the closure of

pulmonary valve (second heart sound) is heard well on this area.

iv. Aortic area

Aortic area is over the right 2nd intercostal space, close to the sternum. On this area, the sound produced

by the closure of aortic valve (second heart sound) is heard well.

First heart sound is best heard in mitral and tricuspid areas. However, it is heard in other areas also but the intensity is less. Similarly, the second heart sound is best heard in pulmonary and aortic areas. It is also heard in other areas with less intensity.


A highly sensitive microphone is placed over the chest. The heart sounds are amplified by means of an amplifier and heard by using a loudspeaker. First, second and third heart sounds are heard by this method.


Phonocardiography is the technique used to record the heart sounds. Phonocardiogram is the graphical record of heart sounds. It is done by placing an electronic sound transducer over the chest. This transducer is connected to a recording device like polygraph. All the four heart sounds can be recorded in phonocardiogram. It helps to analyze the frequency of the sound waves.

Appearance of Heart Sounds in Phonocardiogram

In phonocardiogram, the heart sounds are recorded in the following manner.

First heart sound

First heart sound is recorded as single group of waves. The waves are of small amplitude to start with. Later, the amplitude rapidly rises and falls to form crescendo and diminuendo series of waves. About 9 to 13 waves appear.

Second heart sound

Second heart sound appears as single group of waves, which have same amplitude. About 4 to 6 waves are recorded.

Third heart sound

Third heart sound is found in phonocardiogram with only 1 to 4 waves grouped together.

Fourth heart sound

Mostly, the fourth heart sound merges with first heart sound. If it appears as separate form, it has 1 to 2 waves with very low amplitude

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