Womb Sounds with Heartbeat & Shush

Three familiar comforts in one: the low whoosh of the womb, a calm resting heartbeat, and the soft shush parents use to settle a baby. Made for the newborn weeks, when babies are still getting used to the bright, quiet outside world.

About this sound

Womb layer	Low whoosh (mostly below 450 Hz) that swells gently every 6 seconds
Heartbeat	A calm “lub-dub” at 70 beats per minute, like a resting adult heart
Shush	A soft, rounded “shhh” every 3 seconds, mixed under the womb sound
Filter	5 kHz low-pass, so it stays soft and muffled
Length	10 hours, seamless loop
Screen	Picture for 1 minute, then fades to fully black

What the research says

The womb layer

Before birth, babies hear mainly low sounds; the mother’s body muffles energy above about 500 Hz by 40 to 50 dB ^[1]. Our whoosh sits in that low range.

The heartbeat layer

Very premature babies who heard their mother’s voice and heartbeat, shaped to sound like the womb, for three hours a day developed a larger auditory cortex after a month than babies who heard only hospital noise ^[2]. This was a small study in preterm babies, and long-term effects are unknown.

The shush layer

Shushing is one of the “5 S’s”. In a randomised trial of 230 infants, the 5 S’s together reduced pain scores and crying after vaccinations compared with standard comfort ^[3].

Why we fade to a dark screen

Young children’s body clocks are very sensitive to light in the evening. In a small study of preschoolers (ages 3–5), one hour of bright evening light cut the sleep hormone melatonin by 88%, and it stayed low for at least 50 minutes after the light was switched off ^[4]. A phone screen is far dimmer than that study’s light, and babies were not studied, but the lesson is simple: the less light in the nursery, the better. That is why every Shush Bean video shows its picture for one minute and then fades to a fully black screen.

How loud is too loud

Researchers in Toronto measured 14 infant sleep machines at full volume. At 30 cm (about 1 foot) every one of them was louder than 50 dBA, the limit recommended for hospital nurseries, and three could exceed 85 dBA ^[5]. Their advice: keep the device well away from the crib, keep the volume low, and do not run it at full volume all night. The American Academy of Pediatrics’ safe sleep guidance still comes first: baby on their back, on a firm flat surface, in their own crib or bassinet with nothing else in it ^[6].

How to use it

• Especially popular in the first weeks home, the “fourth trimester”.
• Start it while you feed or cuddle, so it becomes part of the routine.
• Keep the volume low and the device across the room.

Questions

References

1. Gerhardt KJ, Abrams RM. Fetal exposures to sound and vibroacoustic stimulation. Journal of Perinatology. 2000;20(S1):S21–S30. Link
2. Webb AR, Heller HT, Benson CB, Lahav A. Mother’s voice and heartbeat sounds elicit auditory plasticity in the human brain before full gestation. PNAS. 2015;112(10):3152–3157. Link
3. Harrington JW, Logan S, Harwell C, et al. Effective analgesia using physical interventions for infant immunizations. Pediatrics. 2012;129(5):815–822. Link
4. Akacem LD, Wright KP, LeBourgeois MK. Sensitivity of the circadian system to evening bright light in preschool-age children. Physiological Reports. 2018;6(5):e13617. Link
5. Hugh SC, Wolter NE, Propst EJ, Gordon KA, Cushing SL, Papsin BC. Infant sleep machines and hazardous sound pressure levels. Pediatrics. 2014;133(4):677–681. Link
6. Moon RY, Carlin RF, Hand I; AAP Task Force on Sudden Infant Death Syndrome. Sleep-related infant deaths: updated 2022 recommendations for reducing infant deaths in the sleep environment. Pediatrics. 2022;150(1):e2022057990. Link

This page summarizes published research for general information. It is not medical advice. Research on sleep sounds for babies is still limited; talk to your pediatrician about your baby’s sleep and crying.