While it sounds like simple onomatopoeia (a word that sounds like its meaning), "lub dub" is actually the audible sign of your heart valves snapping shut. Here is the simple breakdown of what is happening inside your chest. "Lub dub" is the sound of your heart valves closing. The "lub" happens when the valves between the upper and lower chambers close. The "dub" happens when the valves leading out of the heart to the lungs and body close. The Deep Dive: Act 1 (The Lub) The first sound, the "Lub" (medically known as S1 ), occurs at the beginning of a heartbeat.

Once that blood is pushed out, two different valves—the —snap shut to stop the blood from flowing back into the heart.

You’ve heard the phrase "lub dub" in movies and doctor’s offices, but what does it actually mean? We break down the science behind the heartbeat sound and why it matters. Have you ever been sitting in a quiet room, resting your head on a pillow, and suddenly heard your own heart beating? Lub-dub. Lub-dub. Lub-dub.

It’s one of the most recognizable sounds on the planet. But have you ever stopped to wonder:

Disclaimer: This article is for informational purposes only and does not constitute medical advice. Always consult a qualified healthcare professional for concerns regarding your heart health.

Think of it like a door slamming after a crowd passes through. That sudden tension and vibration of the tissue is the "Lub." Immediately after the squeeze, the heart needs to eject blood out to your body. The right ventricle sends blood to the lungs; the left ventricle sends blood to the rest of the body.