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Decibel Sound Meter

How loud should a white noise machine be for a baby?

There is no single number this app can hand you — it depends on the machine, the room and the distance to the crib — but you can stop guessing by measuring your actual machine, at the actual crib distance, with the phone's Meter tab.

3 min read · Updated 2026-09-17

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Measure the machine where the baby's head actually is

A common mistake is measuring right next to the speaker, which gives a scary-looking number; moving the phone to the actual crib gives something much more reasonable. A white noise machine sounds very different up close than across the room, and sound drops off fast with distance. To get a number that means anything, measure at the crib, not next to the machine, with it set exactly how you'd run it overnight.

Get an honest baseline first

Out of the box the app adds a guessed offset to compensate for phone microphones reading low — +10 dB on iPhone, +8 dB on iPad. For a quiet nursery reading, calibrating in the room first makes the number much more trustworthy:

  1. Open Meter, then tap Calibrate (the tuning-fork button).
  2. With the room quiet and the white noise machine off, tap Auto Calibrate: it takes 30 readings over about 3 seconds and assumes the room is close to 30 dB.
Auto Calibrate, worked example
InputValue
Median reading during calibration50.0 dB
Current Auto Calibration Offset (iPhone default)+10.0 dB
Raw (uncalibrated) reading40.0 dB
New Auto Calibration Offset-8.0 dB
Reading after calibration32.0 dB

Now measure the machine

  1. Turn the white noise machine on at the setting you use overnight.
  2. Hold or place the phone where the baby's head will be, microphone uncovered.
  3. Read the live number on the Meter tab, or tap Start Recording for 30-60 seconds and read AVG for a steadier number than a single instant.
  4. Open the Noise Levels screen to see where that number falls against the app's own everyday-sound list, for a mental anchor rather than a bare number.

If you want a second opinion later in the night, saved recordings go to History with a note and tag (Sleep fits), so you can check whether the machine stayed steady or someone bumped the volume.

Questions and answers

Can I get an alert if the machine is too loud?
The free Noise Alerts threshold is fixed at 85 dB, which is far louder than any reasonable nursery level, so it will not catch this. Premium lets you set a custom threshold from 40 to 120 dB in 5 dB steps if you want a live warning at a lower level.
Does the distance to the crib really matter that much?
Yes. Measuring right next to the speaker instead of at the crib gives a much higher number than the baby actually hears, which is why the app's own reading is only meaningful measured at the real distance.
Can the app tell me the machine is safe?
No. It reports a sound level; it does not know what is safe for a particular baby. Use it to compare settings and distances, and rely on the machine's manual and your paediatrician for the actual recommendation.
Does the app need internet to measure this?
No, measuring and recording work fully offline; only ads, purchases and turning a location into a place name need a connection, and none of those apply to a quick nursery check.

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