A heart murmur sounds like a whooshing or swishing noise between the normal heartbeats. Where a healthy heart produces a clean “lub-DUP” rhythm as its valves open and close, a murmur adds an extra sound, often described as blowing, harsh, or even musical, caused by turbulent blood flow inside the heart. The sound is typically heard through a stethoscope, though the loudest murmurs can occasionally be heard without one.
Normal Heartbeat vs. Murmur
To understand what a murmur sounds like, it helps to know what it’s interrupting. A normal heartbeat produces two distinct sounds: “lub” and “DUP.” The first sound happens when the valves between the upper and lower chambers of the heart snap shut. The second, slightly louder sound comes when the valves leading out to the lungs and body close. Between and around those two sounds, there’s normally silence.
A murmur fills part of that silence with a swooshing, blowing, or rushing noise. Think of it like the difference between water flowing smoothly through a garden hose and water spraying turbulently past a kink. When blood moves in a smooth, orderly stream, it’s quiet. When something disrupts that flow, whether a narrowed valve, a leaky valve, or simply a fast heart rate, the turbulence creates a sound your doctor can hear.
How Murmurs Vary in Sound
Not all murmurs sound the same. Doctors describe them using three main qualities: pitch, tone, and duration.
- Pitch depends on how fast the blood is moving at the point of turbulence. Faster flow produces a higher-pitched sound, while slower flow creates a lower, rumbling quality.
- Tone refers to the character of the sound. Some murmurs sound blowing, like air through pursed lips. Others are harsh and grating. A few are described as honking or even musical, almost like a vibrating string.
- Duration describes how much of the heartbeat the murmur occupies. Some are brief, appearing only in the middle of a beat. Others last the entire time the heart is contracting.
Doctors also grade murmurs on a scale from 1 to 6 based on loudness. A grade 1 murmur is so faint that even with a stethoscope, a doctor may need several seconds of careful listening to detect it. A grade 2 is faint but immediately audible. Grade 3 is moderately loud, grade 4 is loud, and grade 5 is very loud. A grade 6 murmur is so loud it can be heard without a stethoscope touching the chest.
Timing Tells the Story
When the murmur occurs within the heartbeat cycle matters as much as what it sounds like. A murmur that happens while the heart is actively pumping (between the “lub” and the “DUP”) is called systolic. One that occurs while the heart is relaxing and refilling (after the “DUP” and before the next “lub”) is called diastolic. Each pattern points to different things happening inside the heart.
One of the most recognizable systolic patterns is a sound that starts soft, swells louder, then fades again, like a wave building and breaking. This crescendo-diminuendo pattern is the hallmark of a narrowed valve. Blood is being forced through a tighter opening, creating peak turbulence in the middle of the contraction. The more severe the narrowing, the longer the murmur takes to reach its loudest point.
A different systolic pattern is a steady, unchanging whoosh that lasts from the first heart sound all the way to the second, like a constant hiss through the entire contraction. This happens when a valve is leaking backward, allowing a continuous jet of blood to flow the wrong direction for the full duration of the heartbeat. The louder versions of this murmur tend to involve smaller, faster jets of blood, while larger leaks can paradoxically produce a softer sound.
What Innocent Murmurs Sound Like
Many murmurs, especially in children, are completely harmless. These “innocent” murmurs have a recognizable acoustic fingerprint that sets them apart from concerning ones. The most common innocent murmur in children, called a Still’s murmur, has a distinctive low-pitched, musical quality sometimes compared to the sound of a twanging string. It’s typically heard between ages 3 and 6 and disappears by adolescence.
There’s a useful memory device doctors use to recognize innocent murmurs: they tend to be soft, systolic (occurring during contraction), short in duration, confined to a small area of the chest, sweet-sounding rather than harsh, and they appear as a single sound without extra clicks or snaps. They also change noticeably with position and breathing. If you stand up or take a deep breath, an innocent murmur often gets quieter or vanishes. A murmur caused by a structural heart problem typically doesn’t respond that way.
What You Might Actually Hear
If you’ve been told you have a murmur and you’re trying to imagine what your doctor heard, the closest everyday comparison is the sound of air rushing through a narrow space, or water tumbling over rocks in a stream. It’s not a sharp, distinct noise like a click or a snap. It’s a sustained, textured sound layered over the normal heartbeat rhythm.
A soft, blowing murmur might sound like someone gently exhaling through a stethoscope. A harsh murmur has more of a raspy, grating quality, like sandpaper. And those rarer musical murmurs carry an almost tonal, humming character that’s distinct enough for experienced listeners to identify immediately.
The important thing to understand is that the sound itself doesn’t tell you whether a murmur is serious. A loud murmur can be completely innocent, and a quiet one can signal a real problem. What matters is the full picture: the timing, the pitch, the quality, how the sound changes with activity and position, and what an echocardiogram (an ultrasound of the heart) shows about the valves and blood flow. The sound is the first clue, not the final answer.