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Decibo targets ±2 dB(A) accuracy with proper calibration, in line with the NIOSH Sound Level Meter app and the IEC 61672 Type 2 specification. Accuracy depends on (1) calibration vs a known reference, (2) microphone quality of your iPhone model, (3) environmental conditions. The built-in calibration wizard handles (1); newer iPhone Pro models help with (2); choosing a representative ambient sample helps with (3).

Tap Calibrate on the main screen. Two methods: silent-room (Decibo samples 3 seconds in a quiet space and assumes 30 dB SPL) or reference-tone (play a 94 dB SPL reference, e.g. from an SPL calibrator, and Decibo computes the offset). Profiles are named per device and stored locally.

A-weighted (dBA) approximates human hearing — used for environmental noise, OSHA, NIOSH, almost all everyday measurements. C-weighted (dBC) is flatter at low frequencies — used for peak (Lpeak) and industrial high-level measurements. Z-weighted (dBZ) is flat across the spectrum — raw SPL with no weighting.

LAeq: equivalent continuous A-weighted level over the measurement period. Lmax: maximum A-weighted level during the period. LCpeak: C-weighted instantaneous peak. TWA: 8-hour time-weighted average — the OSHA/NIOSH single-number exposure metric. Dose: percentage of permissible daily exposure (100% = at the limit; over 100% = over-exposure).

iOS may route the microphone through your AirPods, hearing aids, or other Bluetooth audio devices instead of the iPhone built-in mic. The frequency response of those devices doesn't match the IEC 61672 mic specification, so readings will be wrong. Tap the warning banner and Decibo forces the iPhone built-in mic.

To measure environmental sound levels in real time. The audio is processed frame-by-frame and never recorded. See Privacy Policy for details.

Settings → Saved sessions → tap a session → Export PDF or Export CSV. The PDF is a one-page report with metrics, time-series chart, and threshold line. CSV is raw time-stamped dB samples for spreadsheet import.

Settings → Restore Purchases. As long as you're signed into the same Apple ID, Pro will unlock automatically.

Apple handles refunds, not us. Go to reportaproblem.apple.com, sign in, and request a refund. Apple usually approves these for legitimate cases. If something specifically is wrong with the app, please email us first — we'd rather fix it.

No. Decibo is a general-purpose environmental and occupational noise meter. It is not for clinical hearing-loss diagnosis, audiology, or medical assessment. For hearing concerns, consult a qualified audiologist or hearing-care professional. For OSHA-regulated workplaces requiring legal compliance documentation, use a calibrated Type 1 sound level meter and follow your jurisdiction's procedure.

Decibo's primary measurement runs on iPhone (AVAudioEngine on the iPhone microphone). A future update may add a Watch companion that displays the iPhone reading remotely.