S1 Heart Sounds


Learn about the S1 heart sound, listen to examples, take short lessons and compare to other heart sounds. For all medical professionals.

Our S1 heart sound lessons can be found in this first heart sounds module. In addition, our reference index is designed to provide quick access to first heart sounds, with audio tracks, listening guides and waveforms. Use this link for quick reference to heart and lung sounds.

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 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 Auscultation

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.

Listen to S1

Listening Tips

Audio Playback

virtual auscultation of patient torso

auscultation position of patient

The patient's position is supine.


Compare To S1 Decreased Intensity

virtual auscultation of patient torso

auscultation position of patient

The patient's position is supine.

S1 Heart Sounds Reference Guide

Our auscultation reference guide provides quick access to this sound as well as many other adventitious sounds. Each sound is described also with an audio recording and waveform.

Authors and Reviewers

Authored by Dr. Jonathan Keroes, MD and David Lieberman, Developer, Virtual Cardiac Patient.
Medically reviewed by Dr. Barbara Erickson, PhD, RN, CCRN.
Last Update: 2/15/2022.
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