Heart sounds

Your heart makes sounds. It goes lub-dub, lub-dub. These sounds come from tiny doors inside.

The doors snap shut to move blood. This helps you stay well.

The first sound is the "lub." It happens when the first set of doors close. This happens when your heart starts to squeeze.

The second sound is the "dub." It happens when the next doors shut. This happens when the heart stops squeezing for a moment.

Sometimes, doctors hear a whoosh. This is called a murmur. It happens when blood flows in a messy way.

Doctors use a tool to listen. It helps them hear your heart. It is good to know your heart is working well.

Your heart makes sounds as it beats. These sounds come from blood moving through your heart.

Most people hear two main sounds. They sound like "lub-dub."

The first sound is called S1. This is the "lub" part. It happens when two doors, called atrioventricular valves, snap shut. These valves include the mitral and tricuspid valves.

As your heart squeezes, these doors close to stop blood from flowing backward.

The second sound is called S2. This is the "dub" part. It happens when the semilunar valves shut. These are the aortic and pulmonary valves.

This sound occurs when the heart stops squeezing for a moment.

Sometimes, doctors hear a different sound. This is called a murmur. A murmur is a whooshing noise. It happens when blood flows in a messy way. This is called turbulent flow. Murmurs can happen for many reasons. Some are normal, but others may mean a valve is not working right. For example, a valve might be too tight. This is called stenosis. Or, a valve might not close well. This is called insufficiency. Doctors use a stethoscope to listen closely to these sounds.

Your heart makes many sounds as it beats. These noises come from blood moving through your heart. Most people hear two main sounds in a sequence. They are often described as a "lub" and a "dub." These sounds happen when heart valves snap shut. This sudden movement creates a vibration in the blood. Doctors use a stethoscope to listen to these sounds.

Listening to these sounds provides important data about your heart.

The first sound is called S1, or the "lub." This sound happens when the atrioventricular valves close. These include the mitral and tricuspid valves. As the heart ventricles begin to contract, pressure builds up. This pressure causes the valves to snap shut. Tiny strings called chordae tendineae help hold the valves. They act like parachute strings to prevent backflow. The S1 sound is actually the sound of blood reverberating.

This happens because the flow of blood is suddenly blocked.

The second sound is called S2, or the "dub." This sound occurs when the semilunar valves close. These are the aortic and pulmonary valves. At the end of a heartbeat, the heart relaxes. As the ventricles empty, the pressure inside them falls. Blood tries to flow backward toward the heart. This backward flow catches the pocket-like valve cusps. The valves snap shut to stop the blood.

This creates the second distinct sound.

Sometimes, doctors hear extra sounds called gallop rhythms. An S3 sound is a third sound. It can sound like "lub-dub-ta." This sound often means there is extra blood volume. An S4 sound is a fourth sound. It can sound like "ta-lub-dub." This sound happens when blood enters a stiff ventricle. Some extra sounds are normal for young people or athletes. However, they can signal heart problems in older adults.

These rhythms help doctors understand heart health.

Doctors also listen for a whooshing sound called a murmur. Murmurs happen because of turbulent flow. This means the blood is moving in a messy way. A murmur can be benign or it can be abnormal. One cause is stenosis, where a valve opening is too tight. Another cause is insufficiency, where a valve does not close well. This allows blood to leak backward. Murmurs can be very faint or very loud.

Doctors use different grades to describe how loud they are.

The human heart produces distinct noises during its rhythmic beating. These sounds are not caused by the muscle itself contracting. Instead, they are generated by the flow of blood through the heart. Specifically, heart sounds reflect the turbulence created when heart valves snap shut. When these valves close suddenly, they cause a reverberation within the blood. Medical professionals use a stethoscope to listen to these sounds. This process, known as cardiac auscultation, provides vital auditory data about heart health.

In a healthy adult, there are two primary sounds. These are often described as a "lub" and a "dub." The first sound, called S1, forms the "lub." It is composed of two parts: the mitral valve closure (M1) and the tricuspid valve closure (T1). Usually, the mitral closure happens slightly before the tricuspid closure. S1 occurs at the beginning of ventricular contraction, or systole. As the ventricles contract, they squeeze against the closed semilunar valves. This pressure sends blood rushing toward the atria. The parachute-like leaflets of the atrioventricular valves catch this rush and snap shut.

To prevent these valves from turning inside out, the heart uses a special mechanism. The papillary muscles in each ventricle contract at the same time as the ventricles. These muscles are attached to the valve leaflets via chordae tendineae, often called heart strings. When the muscles contract, the chordae tendineae become tense. This prevents the valves from evertng, which means they won't bulge too far into the atria. This tension ensures that blood cannot flow backward into the lower-pressure atria. The S1 sound itself is the result of the blood reverberating after this sudden block of flow.

The second heart sound is called S2, or the "dub." This sound marks the end of ventricular systole and the start of ventricular diastole, which is the relaxation phase. S2 is composed of the aortic valve closure (A2) and the pulmonary valve closure (P2). Normally, the aortic closure precedes the pulmonary closure. As the left ventricle empties, its internal pressure falls below the pressure in the aorta. This causes blood to flow quickly backward toward the ventricle. The pocket-like cusps of the aortic valve catch this blood and snap shut. A similar process happens with the pulmonary valve as pressure falls in the right ventricle.

Sometimes, the S2 sound can be "split." A physiological split is normal and often occurs during inhalation. During inhalation, a decrease in intrathoracic pressure increases the time needed for pulmonary pressure to exceed right ventricular pressure. However, a wide and fixed split can indicate an atrial septal defect. Other conditions, such as pulmonary stenosis or a right bundle branch block, can cause a wide and variable split. In cases of pulmonary hypertension or pulmonary embolism, the pulmonary component (P2) may sound much louder than usual. Conversely, aortic stenosis can make the S2 sound much softer.

Beyond the normal sounds, doctors may hear extra sounds called gallop rhythms. An S3 sound, or "ventricular gallop," sounds like "lub-dub-ta." It occurs at the beginning of diastole when blood rushes into the ventricles. While S3 can be benign in young people or athletes, it may signal heart failure in older adults. An S4 sound, or "atrial gallop," sounds like "ta-lub-dub." This sound occurs when blood is forced into a stiff or hypertrophic ventricle. S4 is generally a sign of a pathologic state, such as systemic hypertension. If S3 and S4 are both present, it is called a quadruple gallop.

Another common finding is a heart murmur. Murmurs are whooshing sounds produced by turbulent blood flow. For a murmur to be audible, there must be a pressure difference of at least 30 mm of Hg between chambers. Turbulence can be caused by stenosis, where a valve opening is too narrow, or insufficiency, where a valve fails to close properly. If turbulence occurs outside the heart, it is called a bruit or vascular murmur. Doctors grade murmurs from 1 to 6. A Grade 1 murmur is very faint, while a Grade 6 is so loud it can be heard even when the stethoscope is partly off the chest.