Decibel Shield
How accurate is the Apple Watch Noise app?
Close to a professional meter in the two published tests. In 13 real settings from 35 to 110 dBA, an Apple Watch Series 6 read 0.5 dBA below a class 1 sound level meter on average, with 95% of readings between 3 dBA above and 4 dBA below it. Apple publishes no accuracy figure of its own.
Last updated:
What does the Noise app measure?
The Noise app uses the watch’s microphone to measure the sound level around you in A-weighted decibels, and how long you are exposed to it. The watch measures periodically through the day while you wear it. If the average level over three minutes reaches the threshold you chose, the watch taps your wrist (Apple: Use the Noise app; Apple Watch User Guide).
Levels below 80 decibels show as OK and levels above it as Loud. The readings are kept in the Health app on your iPhone under Hearing, Environmental Sound Levels.
How accurate is it in tests?
Two peer-reviewed tests have compared the watch with a class 1 sound level meter, the most accurate grade.
In real places. Researchers at the University of Bern wore an Apple Watch Series 6 beside a class 1 meter in 13 settings, among them an office, a restaurant, a street, a construction site, a concert and a music club, at levels from 35 to 110 dBA (Fischer et al., Frontiers in Neurology 2022; PubMed). Across 156 paired measurements the watch read 0.5 dBA lower than the meter on average. The spread was wider than the average suggests: 95% of the differences fell between the watch reading 3.0 dBA higher and 4.0 dBA lower than the meter. The authors had set ±2 dBA as their target, the tolerance of a class 2 meter, and only the concert and train station settings met it.
In a sound booth. A team at the University of California, Irvine played pure tones from 125 to 8,000 Hz at 21 loudness steps to a Series 6 and a class 1 meter side by side (Muhonen et al., JAMA Otolaryngology 2023; open copy). The two agreed closely at most frequencies (at 1,000 Hz the averages were 86.57 and 86.99 dB). The watch differed significantly at two: it read about 6 dB high at 4,000 Hz and about 4.5 dB low at 8,000 Hz.
The Bern authors conclude that the watch is accurate enough to raise awareness of hazardous noise, and that professional and legally binding measurements need a sound level meter or a dosimeter. The Irvine authors add a limit of their own test: it used pure tones in a booth, which real noise rarely is.
What does Apple say about accuracy?
Apple gives no accuracy figure and no measuring range for the Noise app. It does say that water and wind can affect the accuracy of sound levels, and that measurements are suspended while the watch is in Water Lock or while the microphone or speaker is in use (Apple: Use the Noise app).
Which decibel levels does it warn about?
You choose the threshold in the Watch app (My Watch, Noise, Noise Threshold) or on the watch (Settings, Noise). Apple’s table for the levels it covers:
| Level | Time in a day that can cause temporary hearing loss | Weekly limit |
|---|---|---|
| 80 dB | About 5 hours 30 minutes | 40 hours |
| 85 dB | About 1 hour 45 minutes | About 12 hours 30 minutes |
| 90 dB | About 30 minutes | 4 hours |
| 95 dB | 10 minutes | About 1 hour 15 minutes |
| 100 dB | A few minutes | About 20 minutes |
The weekly column follows the World Health Organization and ITU safe listening standard, which allows 80 dB for 40 hours a week and halves the time for every 3 dB above that (WHO). For the wider picture, see what decibel level is dangerous.
Does the Noise app record what it hears?
No. Apple says the watch samples the microphone to measure the level and does not record or save any sounds (Apple Watch User Guide).
Which Apple Watch models have the Noise app?
It arrived with watchOS 6 in 2019. Apple’s user guide lists Apple Watch SE and Apple Watch Series 4 and later (Apple Watch User Guide, watchOS 7).
Where does the watch fall short?
- It measures at your wrist. The booth study’s authors point out that sound at the wrist is not the same as sound at the ear, and that a sleeve or wind can interfere with the microphone.
- It samples, it does not listen continuously. The Bern team found the watch returned a level about every second in loud places and as rarely as every 35 seconds in quiet ones, so a short loud event in a quiet setting can be missed.
- Each test used a single watch. Both were a Series 6, so newer models are untested in print.
- It is not evidence. For a workplace or legal measurement the authors of the field study recommend a sound level meter or a dosimeter.
To check a reading from the watch, or to measure without one, the free online decibel meter runs in a phone or computer browser and shows the minimum, average and maximum of a session. See also can your iPhone measure decibels?
