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Normal Heart Sounds
Educational only: videos on MedicalVideos.com are for general information and are not medical advice. Always consult your own doctor about your health.
Normal Heart Sounds With the aid of a stethoscope you can hear the characteristic sounds of the normal heartbeat, typically described as a "lub-dub." These sounds are produced by the closure of the heart valves. The first heart sound or "lub" results from closure of the tricuspid and mitral valves. It is a rather low-pitched and a relatively long sound which, as indicated in, represents the beginning of ventricular systole. The second heart sound, or "dub," marks the beginning of ventricular diastole. It is produced by closure of the aortic and pulmonary (pulmonic) semilunar vanes when the intraventricular pressure begins to fall. This "dub" sound is typically heard as a sharp snap because the semilunar valves tend to close much more rapidly than the AV valves. Because diastole occupies more time than systole, a brief pause occurs after the second heart sound when the heart is beating at a normal rate. Therefore, the pattern that one hears is one of: "lub-dub" pause, "lub-dub" pause, and so on. Sometimes, especially in young normal individuals, a third heart sound can be heard. This sound is produced by the very rapid influx of blood into the partially filled ventricle. It is typically very faint and as such difficult to hear.
This video in 30 seconds
This short narrated lesson reviews normal heart sounds before auscultation. It explains how closure of the heart valves produces the first and second sounds, S1 and S2, and how systole and diastole fall between them. It also names the chest areas where the sounds are heard, including the aortic, pulmonic, tricuspid, and mitral areas.
Key points
- The narration links S1 to mitral valve closure and S2 to aortic valve closure
- Systole is described as occurring between S1 and S2, with diastole following S2
- Diastole is noted as usually lasting longer than systole
- The aortic and pulmonic areas are described together as the base of the heart
- Auscultation locations at the sternum and apical impulse are identified
Video Transcript
A short narrated lesson on normal heart sounds. It explains how the closing of the heart valves produces the first and second sounds, S1 and S2, the difference between systole and diastole, and the chest locations where the sounds are best heard — the aortic, pulmonic, tricuspid, and mitral areas.
Read the full transcript
Before auscultating the heart, let's review normal heart sounds. Closure of the heart valves creates a pair of audible heart sounds. The first sound, S1, accompanies mitral valve closure. The second sound, S2, accompanies aortic valve closure. Pulmonic and tricuspid valve closure may contribute to these sounds. Ventricular systole occurs between S1 and S2. Ventricular diastole occurs between S2 and the next S1. Because diastole usually lasts longer than systole, you can identify the two sounds. One-two, one-two, one-two. You can hear S1 and S2 in the aortic area in the right second interspace close to the sternum.
Pulmonic area in the left second interspace close to the sternum. Left third interspace. Tricuspid area in the left fourth and fifth interspaces. And mitral area at the apical impulse. The aortic and pulmonic areas together are sometimes called the base of the heart.
Transcript auto-generated from the video’s audio for accessibility and study. Educational content only — not medical advice.
Video Overview
From our Cardiology collection: ECG interpretation, echocardiograms, angioplasty, stents and heart conditions explained by cardiologists. Browse all Cardiology videos →
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