Test how loud your restaurant is. Your neighbor's late-night party. Your concert. Your office HVAC. Your baby room. Apple's iPhone has no sound level meter (the Watch one reads 3.4 dB low per NIH research). The popular third-party apps charge around $40/year and read 28 dB in a completely silent room.
Decibo is what those apps should have been.
What it measures
A / C / Z frequency weighting (IEC 61672)The three standard curves: A for environmental + occupational, C for peak / industrial, Z for raw SPL.
LAeq, Lmax, LCpeak, TWA, DoseThe metrics OSHA and NIOSH actually require for occupational noise tracking.
30 ISO 1/3-octave bands, 25 Hz to 16 kHzSpectrum view shows which frequencies dominate — useful for HVAC, motor noise, voice noise, music levels.
What makes Decibo different
Real zero calibrationTwo-mode silent-room and reference-tone calibration. Saved profiles per device. Fixes the "28 dB in a silent room" problem.
8 scene presetsWorkplace, concert, sleep room, baby room, restaurant, office, HVAC, studio — each with calibrated threshold, weighting, and concise OSHA/NIOSH/WHO advice.
Threshold alarmHaptic + optional notification when sound crosses your scene's limit. For concert hearing protection, OSHA shifts, baby sleep, etc.
Live Activity in Dynamic IslandLong sessions show current dB + LAeq + dose on the lock screen and Dynamic Island.
Session history with iCloud syncEvery recorded session is saved; sync across your iPhone and iPad.
PDF + CSV exportFormatted PDF reports for noise complaints, real estate inspections, OSHA records.
Bluetooth-mic warningDetects when hearing aids or AirPods take over the iPhone mic — and lets you switch back with one tap.
Audio file import + analysisDrop in a voice memo, recording, or any .m4a / .wav / .mp3 — Decibo computes LAeq / Lmax / Lpeak offline.
Apple Shortcut + Action ButtonOne-tap measurement from anywhere (iPhone 15 Pro and later).
Dark mode, big buttons, VoiceOver, Dynamic TypeBuilt for accessibility — every text scales, every button labeled, every action haptically reinforced.
100% on-device
The microphone audio never leaves your iPhone. No server. No third-party SDK. No tracking. AVAudioEngine captures, Accelerate processes A/C/Z weighting and FFT, SwiftUI renders. The Privacy Nutrition Label says "Data Not Collected" because it doesn't.
Pricing
Free trial: 5 days × 20 minutes a day. No card. No sign-up. Pro unlocks unlimited daily time, all 8 scenes, threshold alarm, Live Activity, history sync, PDF/CSV export, alt app icons, and audio-file import — for $3.99 once. No subscription. Ever.
Decibo is an environmental and occupational sound level meter. It is not a medical device, not a substitute for calibrated professional equipment, not for clinical hearing-loss diagnosis. For hearing concerns, consult an audiologist or hearing-care professional.