How far should a sound machine be from a baby’s crib?

Author LullasureReviewer pediatric audiologist review pendingSources reviewed 2026-09-03

Direct answerStands on its own

As far as the room allows. The AAP says to place infant sleep machines as far away from the baby as possible, at the lowest effective volume, for a limited time. In practice that means across the room, never on the crib, and confirmed with a quick check at mattress height before you put the baby down.

What this does not mean: There is no universal distance in centimeters because speakers, rooms, and volume settings differ. Distance is one lever; volume and duration are the others.

Why distance changes what your baby hears

Sound energy spreads out as it travels. Moving a small speaker from 30 cm to 1 m from the mattress can reduce the level at the mattress by a noticeable margin, and reflections from walls and furniture change the result further. This is exactly why a phone sitting beside the speaker cannot tell you what is happening at the crib.

Placement checklist

Never in or on the crib. No devices, cords, clips, or mounts on the rail.
Across the room on a dresser or shelf, pointed away from the crib if the speaker is directional.
Lowest effective volume, confirmed with a check at crib height with the crib empty.
Recheck after any change: a new speaker, a moved dresser, a different sound, or a Bluetooth route.

Our distance experiment

We are running a controlled experiment comparing white, pink, and brown noise at 30 cm, 1 m, and 2 m from a mattress-height microphone, across several iPhone models and common nursery machines, against a calibrated reference meter. Results, raw data, and the chart will be published on the calibration page when the lab session is complete. We will not publish estimated numbers before then.

Sources

Follow-up questions

Can I put the sound machine under the crib?

It keeps the device out of reach, but it does not make it distant. Measure at mattress height; the level there is what matters.

Does a bigger room mean I can turn it up?

A bigger room usually lowers the level at the crib for the same setting. Check rather than assume.