Use a Decibel Meter in Safari
A web decibel meter uses the same microphone as any app. Open the decibel meter in Safari or Chrome and follow these steps:
- Tap Start Measuring, then tap Allow when Safari asks for the microphone.
- Hold the phone with the microphone pointing at the sound, away from your body.
- Read the live level. Avg shows the average (Leq) since you started, and Reset clears it.
The sound is analyzed on the phone, in the browser, and nothing is recorded or uploaded. For a place with its own rules, use a preset such as the workplace noise meter, which compares the reading with the 85 dBA limit.
How Accurate an iPhone Reading Is
Phone microphones vary, so an uncalibrated reading is usually within 5 to 10 dB. Calibrate once against a hardware sound level meter, using Calibrate and Settings, and readings are typically within 1 to 2 dB for everyday sounds. Sounds above about 100 dB can overload a phone microphone. The accuracy page explains how to calibrate and where phone meters fall short.
NIOSH, the US agency for workplace safety research, tested its own app the same way. It reports the NIOSH Sound Level Meter app as accurate within ±2 dBA in its acoustics lab. With a calibrated external microphone, NIOSH says the app meets the Type 2 requirements of the IEC 61672-3 standard. That standard is the one handheld meters are built to; see types of sound level meters. For a reading that has to stand up at work or in a complaint, see our sound level meters guide.
The NIOSH Sound Level Meter App
The NIOSH SLM app is free and made for iOS only: NIOSH says it can't yet verify Android versions. Beyond the live level, it shows:
- LAeq (the average level) and the time-weighted average (TWA) used for workplace limits.
- Maximum and peak levels.
- Noise dose and projected dose.
- A, C, and Z weighting. See what dBA means for the difference.
It can calibrate either the built-in microphone or an external one. It suits checking a job against the 85 dBA limit; for a quick reading anywhere, the browser meter needs no install.
What the iPhone Measures by Itself
iPhone has a decibel readout, but it is for headphones.
Add the Hearing control to Control Center (tap the add button at the top left, then Add a Control, then Hearing under Hearing Accessibility). Tap it while music plays and the Headphone Level meter shows the audio level in decibels. Apple says this monitor is meant for audio playback, and that its readings are most accurate with Apple or Beats headphones. With other headphones, the level is estimated from the iPhone's volume.
Two related settings live in Settings, Sounds & Haptics, Headphone Safety. Headphone Notifications warn you when you have listened loud for long enough to affect your hearing. Reduce Loud Audio lowers any headphone sound above the level you pick. The Health app keeps the history under Browse, Hearing.
Apple Watch Noise App
An Apple Watch measures the room around you with its Noise app. It checks sound levels from time to time while you wear it, using the microphone without recording or saving any sound. Apple marks levels below 80 dB as OK and above 80 dB as Loud. The watch can also tap your wrist when the average over three minutes reaches a threshold you choose. Your iPhone keeps the readings in the Health app as Environmental Sound Levels.
For how long a level is safe, see how loud is too loud.