DecibelwerkQuick answer: Decibelwerk turns your iPhone into a sound level meter with a backlit VU needle. It reads the microphone in iOS measurement mode, applies A, C or Z weighting, and shows the live level, the average (Leq), the minimum and maximum, and how long NIOSH says is safe at the current level. The meter is free.
What’s on the panel
- VU needle on a backlit cream face, 30 to 120 dB, with the red zone starting at 85 dB, where NIOSH starts counting the clock.
- Amber readout with the live level to a tenth of a decibel, plus Leq, MAX and MIN since you last pressed RESET.
- WEIGHT selector: A (free), C and Z (Pro).
- RESPONSE selector: Fast or Slow.
- NIOSH limit for the reading: 8 h+ below 85 dBA, 1 h at 94, 15 min at 100.
- HOLD freezes the display so you can read it off or take a screenshot.
- REC LOG starts a noise log that records the level once a second.
How accurate a phone can be
iPhones use good MEMS microphones, and measurement mode stops iOS from turning quiet sounds up. In ordinary rooms, readings usually land within a few decibels of a dedicated meter. Two limits are worth knowing:
| Range | What to expect |
|---|---|
| Below about 35 dB | The microphone’s own noise floor starts to show; very quiet rooms read high. |
| 35–110 dB | The useful range for homes, venues, offices and workshops. |
| Above about 110 dB | Phone microphones can start to compress, so peaks may read low. |
If you have access to a calibrated meter or a 94 dB calibrator, Pro’s CAL knob trims readings by up to 10 dB in half-decibel steps. The step-by-step method is in how to measure decibels on iPhone.
Free and Pro
The live meter, A-weighting, Fast/Slow, HOLD and RESET are free with no time limit. Pro adds C and Z weighting, calibration, unlimited noise logs and PDF reports.