The first sound in the cycle, known clinically as , is the "lub". This sound marks the beginning of ventricular systole , the phase where the heart's lower chambers (ventricles) contract to pump blood out to the body and lungs.
// helper: simple beep with decay (lub = lower freq, dub = higher + shorter) function playLub() if (audioCtx.state === 'suspended') audioCtx.resume(); lub dub valves
The second sound, the (medically known as S2 ), is shorter, sharper, and higher-pitched. The first sound in the cycle, known clinically
The second sound, or , is the "dub". This sound occurs at the end of ventricular systole and the beginning of ventricular diastole , when the heart relaxes to refill with blood. The first sound in the cycle