Womb Sound Generator
The sound a baby heard before birth, built from three parts: a heartbeat near 70 beats per minute, the slow whoosh of blood flow, and a low bed under both. Press Play, set a timer, and put the device across the room.
This sound is generated in your browser as it plays. It is not a recording, so nothing streams and nothing is downloaded.
The heartbeat is scheduled beat by beat with a small 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. Every one exceeded 50 dBA at 30 cm at maximum volume and three exceeded 85 dBA. The authors advise distance from the crib, low volume and limited playing time.
The American Academy of Pediatrics does not endorse white noise for babies. Its 2023 policy on noise exposure urges caution and asks pediatricians to talk to parents about safe use of sleep machines.
One small study from 1990 reported that 80% of 40 newborns fell asleep within five minutes with white noise, against 25% without. Forty babies is far too few to settle the question.
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
What you are hearing
Three layers play together. A low brown noise bed carries the body of the sound. A second bed moves under a slow filter sweep, which is the blood flow whoosh. Over both, a lub-dub pair fires near 70 beats per minute, the maternal rate, with a few percent of variation from beat to beat.
How parents use it
Start it while you settle your baby, then let the sleep timer take it away. Settle mode begins 6 dB above your volume to cut through crying and steps back down over six minutes. Keep the device at least 2 m (7 ft) from the crib.
What it is not
This is a synthesised approximation, not a recording of a womb and not a medical instrument. It masks the sounds of a room. Whether that suits your baby is something only you can judge.
Frequently asked questions
What does a womb actually sound like?
Recordings made inside the uterus are dominated by a low, muffled rush of blood with a steady maternal heartbeat over it, most of it below a few hundred hertz. This tool builds that shape from filtered noise and scheduled beats, so it is an approximation rather than a recording.
How loud should it be?
Aim for about 50 dB at your baby's ear, roughly the level of a quiet conversation, with the device at least 2 m (7 ft) from the crib. Use the lowest volume that works. The safety note on this page carries the sources.
Can it play all night?
Published guidance advises against it. Use the sleep timer instead: it fades the sound out over the last 30 seconds and then stops. The countdown runs on the clock, so it keeps working while this tab sits in the background.
When should we stop using it?
There is no evidence-based age. Many families taper it off as sleep settles. At any age the advice is the same: low volume, distance from the crib, and limited playing time. Ask your pediatrician about your own baby.