Choose the measurement before trusting the number
The free NIOSH Sound Level Meter app offers A-weighted averages and other metrics. NIOSH reports accuracy within ±2 dBA for its tested app and Type 2 requirements with a calibrated external microphone. Those statements describe a particular measurement system; they are not a promise about every decibel app or every nursery condition. NIOSH documentation.
Look for the app’s supported hardware, tested sound-level range and calibration information. A polished dial or extra decimal place tells you little about measurement quality. If two apps disagree, picking the lower result does not resolve the disagreement.
A repeatable check with the crib empty
If a phone is also the sound source, keep that phone at the intended speaker location and use another device to measure. Moving the playing phone into the crib changes the setup you meant to check. A second device does not have to use the same brand of app, but its measurement documentation still matters.
- Leave the sound machine in its normal position and select the actual sound and volume you intend to use.
- Check near the position where the baby’s head would be, at mattress height. Keep fingers, clothing and bedding away from the microphone. Follow the meter’s orientation instructions.
- Keep the checking phone still and avoid talking or handling it during the sample. Record any door slam or other interruption instead of silently treating it as the machine’s output.
- Use a consistent observation period, such as 30 seconds for a steady sound. Record whether the app displays a live level or an average; watching a live number for 30 seconds does not turn it into an average. This interval is a practical comparison choice, not an AAP requirement.
- Write down the result and its metric, then change one setting and repeat in the same position. Remove the measuring phone before the baby uses the crib.
Which number should you write down?
LAeq represents an A-weighted average over the measurement period. Maximum and peak measurements answer different questions, and workplace dose calculations use occupational assumptions. Check the labels rather than treating every displayed “dB” value as interchangeable. NIOSH meter help guide.
A steady sample is useful for a steady machine. It cannot tell you about a track transition that happened later or music someone turned up after you left. Recheck when the setup changes instead of treating a saved result as permanent.
Changing from white to pink or brown noise also changes the sound you are checking. Our noise color explanation separates the frequency balance from exposure level and measurement weighting.
| Detail | Example of what to record |
|---|---|
| Metric | LAeq, not just “decibels.” |
| Time | The actual sample duration. |
| Hardware | Phone model and any external microphone. |
| Setup | Sound, volume and both device positions. |
| Conditions | Door open, fan running, or an interruption. |
What a home comparison can and cannot establish
Calibration compares a reading with a known reference. The NIOSH guide describes a calibrated meter or an acoustic calibrator; ordinary conversation is not a reference of known level. Calibration instructions. Do not enter an offset simply to make your nursery match a number from a search result.
Our first comparison with NIOSH found a large scale error on one phone and estimated a provisional correction. It publishes the setup, paired readings and limits; a comparison between apps cannot establish independent instrument accuracy.
Lullasure’s device calibration and laboratory uncertainty validation remain incomplete as of this source check. Its current Check screen displays a live estimate. Treat that number and its guidance bands as unvalidated; they do not establish an absolute sound level or hearing safety. See the calibration page for the status and limits.
Common questions
Does the AAP require a 30-second sound check?
No. A consistent sample can help compare steady sounds, but no 30-second clinical safety test is established here. Lullasure Check shows a live estimate, not a completed 30-second test.
Can I calibrate an app using another phone?
Agreement between two unvalidated phones does not establish accuracy. A calibration needs a documented reference, not a second unknown reading.
Sources and updates
- NIOSH Sound Level Meter app: capabilities and testing
- NIOSH Sound Level Meter Application Help Guide — Metric definitions and reference-based calibration.
- Lullasure calibration status — Product disclosure, not independent validation.
: Linked the September 9 home comparison with NIOSH and clarified how an app comparison differs from independent instrument validation.
Found a problem? Send a correction with the page and source.