Heartbeat Sound
A lub-dub heartbeat at the rate you pick, from 60 to 150 beats per minute, with a soft low bed under it. The maternal rate a baby heard before birth sits near 70.
This sound is generated in your browser as it plays. It is not a recording, so nothing streams and nothing is downloaded.
Every beat is scheduled on its own with about 3% of variation in the timing, so the rhythm never repeats exactly.
The sound keeps playing with the screen off or locked wherever the browser allows it, and your lock screen gets a play and pause control. Some phones stop background audio anyway, so try it on your own device before you count on it for a whole night.
Everything runs in your browser. Nothing is uploaded, nothing is stored on a server.
Sound fades in when you press Play and fades out when you stop.
Audio starts on your first tap on Play, as required by your browser.
Playing sound near a baby
Sound machines are common and the evidence behind them is thin. These are the precautions the published guidance supports.
- Keep the sound near 50 dB at the baby's ear. That is about as loud as a quiet conversation.
- Put the device at least 2 m (7 ft) from the crib, and never inside it.
- Use the lowest volume that settles your baby. Louder is not better.
- Use the sleep timer instead of playing all night, and turn the sound off once your baby is asleep.
- Phone and tablet speakers vary, so the volume slider on this page is not a level meter. A free sound level meter app gives you a rough check at the crib.
A 2014 study in Pediatrics measured 14 infant sleep machines and found every one could exceed 50 dBA at 30 cm at maximum volume, which is why the precautions above are about distance, level and playing time. The American Academy of Pediatrics does not endorse white noise for babies and asks for caution, and the one small trial people cite in its favor covered only 40 newborns; all three sources are below.
This page is not medical advice and these tools treat nothing. They mask other sound, and many parents find that soothing. Ask your pediatrician about your own baby.
Sources
How it is made
Every beat is a pair. The lub is a low thump near 52 Hz. The dub follows about a quarter of the way through the beat, 4 dB quieter and a little higher. Both are noise through a narrow filter with a fast attack and a short decay, and a quiet brown noise bed sits underneath.
How parents use it
Set the rate near 70 for the womb-like version, or match whatever settles your baby. Arm the sleep timer, turn settle mode on so it starts louder and steps down, and keep the device across the room.
What it is not
This is a synthesised pulse, not a recording of a heart and not a fetal monitor. It carries no information about anyone's heart and it diagnoses nothing.
Frequently asked questions
Which BPM should I choose?
A resting adult heart runs near 60 to 80, and 70 is the usual reference for a womb sound. Faster rates read as more urgent. Pick what settles your baby; there is no researched number for this.
Is this a real heart recording?
No. Both beats are generated from filtered noise with a short envelope. It approximates the sound of a heartbeat and nothing more.
How is this different from the womb sound?
The womb sound puts the same heartbeat under a blood flow whoosh and a heavier low bed, fixed near 70 BPM. This page gives you the beat on its own with the rate in your hands.
What level should I set the heartbeat to?
Judge it by the beat, not by the bed underneath. Each thump peaks above the low hum it sits on, so a mix that measures right on average can still be sharp at the moment of the beat. Set the level from across the room, at least 2 m (7 ft) from the crib, and keep the peaks near the 50 dB the guidance asks for. The safety note above carries the sources.