S1 Heart Sound Page

Welcome to the S1 heart sound page. On this page we provide a definition, sample heart sounds and links to the training lessons available on this site.

What is an S1 Heart Sound?

S1 heart sound is a low frequency sound, occurring at the beginning of systole. S1 can be best heard over the apex, using a stethoscope's bell or diaphragm. The first heart sound is caused by turbulence created when the mitral and tricuspid values close. S1 and S2 heart sounds are often described as lub - dub.

S1 & S2 Heart Sounds Audio

S1 and S2 Normal

Click to play.

S1 (Loud)

S1 Heart Sound Caused By

The S1 heart sound is caused by blood flow turbulence when mitral and tricuspid valves close at the start of systole.

Best Heart Position During Ausucultation

Because S1 heart sounds occur when the mitral and tricuspid valve close, the best heart is locations for the stethoscope chestpiece are at the tricuspid (left lower sternal border) and mitral (cardiac apex) locations.

Normal Heart Sound Guide

Our auscultation guide provides information and examples of S1 (and S2) hearts sounds. The guide pages provide waveforms with a moving cursor that is synchronized to the audio recording. In addition, listening tips are available.

Normal Heart Sounds

S1 Heart Sound Courses

This is a link to our short courses that cover first heart sounds.
Normal Heart Sounds
First Heart Sounds