This beginner-friendly explainer walks through every heart sound — normal and abnormal — with real audio examples so you can hear the difference.
Heart symptoms and treatment decisions should be evaluated by a qualified clinician, especially when symptoms are new, severe, or worsening.
Overview
This beginner-friendly explainer walks through every heart sound — normal and abnormal — with real audio examples so you can hear the difference.
Key Details
The cardiac cycle has two main phases: systole (contraction) and diastole (relaxation). Blood flows from the atria into the ventricles, then the ventricles pump it out — right side to the lungs, left side to the body. S1 ('lub') is the first heart sound, produced when the AV valves (tricuspid on the right, mitral on the left) shut at the beginning of systole. This prevents blood from flowing backward into the atria. S2 ('dub') is the second heart sound, produced when the aortic and pulmonary (pulmonic) valves close at the beginning of diastole after the ventricles have ejected blood. Together they create the familiar lub-dub rhythm.
Why It Matters
S3 is a third sound heard just after S2, caused by blood rushing into the ventricle during early diastole. It's normal in children and young adults but can signal heart problems in older adults. The mnemonic is 'Ken-tuc-ky' to remember the timing. It's also called a ventricular gallop. S4 is a fourth sound heard just before S1, caused by the atria pushing blood into stiff ventricles late in diastole. The mnemonic is 'Ten-nes-see.' This is usually a sign of cardiac problems — the ventricle wall is stiffer than normal, so blood bouncing against it creates the extra sound. It's also called an atrial gallop.
Key Takeaways
- S1 ('lub') = AV valves closing at the start of systole; S2 ('dub') = aortic and pulmonary valves closing at the start of diastole
- S3 (ventricular gallop, 'Ken-tuc-ky') is normal in children but a warning sign in adults — it's blood rushing into the ventricle during early filling
- S4 (atrial gallop, 'Ten-nes-see') means stiff ventricles — blood pushed by the atria bounces against a rigid wall, usually indicating cardiac problems
- Heart murmurs are whooshing sounds from turbulent flow through leaky or narrowed valves — systolic murmurs are most common, diastolic are less common but can be more serious
- Hearing an abnormal sound alone doesn't confirm a problem — professional evaluation determines whether treatment is needed
FAQ
What does this page explain?
It explains heart sounds explained — s1, s2, s3, s4, and murmurs with audio examples in plain English, focusing on the main symptoms, mechanisms, or treatments described in the source content.
When should medical care be sought?
Urgent or severe heart-related symptoms should be assessed right away rather than managed only with online information.
What is the main takeaway?
The main takeaway is to understand the condition or emergency clearly and connect it to prompt evaluation, treatment, or prevention where appropriate.
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