What Is Lub Dub Sound ((new)) May 2026

LUB (ventricles squeeze, AV valves close) → DUB (ventricles relax, semilunar valves close) → pause (heart fills with blood) → LUB ... Part 4: Lub-Dub vs. Dub-Lub (A Common Confusion) People often ask: Why is it "lub-dub" and not "dub-lub"?

But what exactly causes these two distinct sounds? Why doesn't the heart make just one sound? And what happens when "lub-dub" turns into something else, like a "whoosh" or a "click"? what is lub dub sound

In short: (AV valves close). Dub (Semilunar valves close). Pause (Heart refills). Repeat 60–100 times per minute. That is the rhythm of life. LUB (ventricles squeeze, AV valves close) → DUB

The order is based on the in the heart cycle. Systole (contraction) always comes before diastole (relaxation). The AV valves (lub) must close at the start of contraction. The semilunar valves (dub) close at the end of contraction. But what exactly causes these two distinct sounds

A murmur is a valve closing. It is the sound of turbulent blood flow .

If you’ve ever listened to a healthy heart through a stethoscope, the sound you hear is a familiar, two-beat rhythm: lub-dub, lub-dub, lub-dub . This is not just a random noise; it is the acoustic signature of your heart valves snapping shut. It is the sound of life itself.

During diastole, the ventricles are relaxing and filling with blood from the atria. No major valves are snapping shut, so there is no loud sound. This silence is just as important as the beats, because it is the time when the heart refills for the next pump.