Lub-dub Sounds -

A slightly lower-pitched, longer "lub."

The powerful lower chambers of your heart (the ventricles) begin to contract. This sudden spike in pressure slams shut the two top valves: the Mitral and Tricuspid valves. These valves separate the upper chambers (atria) from the lower chambers. When they close, they vibrate, creating that thudding "lub" sound.

Thump-thump. Thump-thump.

Spoiler alert: It’s not the heart muscle contracting, and it’s not the blood whooshing around.

After the heart squeezes blood out to the lungs and body, the ventricles relax. The blood in the major arteries (the Aorta and Pulmonary Artery) wants to rush back into the heart, but two different valves—the Aortic and Pulmonary valves—snap shut to stop it. Their closure creates the "dub." lub-dub sounds

Think of your heart as a house with four rooms (chambers) and four doors (valves). To get blood moving in the right direction, those doors must open to let blood through and then slam shut to prevent it from leaking backward. The "lub" and "dub" are the sonic booms of those doors closing. The first sound, "Lub" (clinically known as S1 ), marks the beginning of systole —the moment your heart squeezes blood out to the body.

That longer rest is crucial. It’s the moment when the heart fills up with blood again, preparing for the next "lub." Sometimes, a doctor doesn't hear a clean "lub-dub." Instead, they hear a "lub- shhh -dub" or a "lub-dub- whoosh ." This is called a heart murmur . A slightly lower-pitched, longer "lub

A sharper, higher-pitched, shorter "dub."