NoiseLedger: Decibel Meter

Pro noise metrics that other apps charge for: NIOSH/OSHA dosimeter, percentiles, spectrogram, third-octave bands and multi-page PDF reports. Free, no ads, fully offline.

NoiseLedger is a privacy-first decibel meter and noise log for iPhone. Measure sound levels in real time, run overnight recordings, and export professional reports — with no ads, no account, no subscription, and no cloud.

MEASURE WITH CONFIDENCE • Real-time dB with FAST/SLOW response, MIN / Leq / MAX • A, C and Z frequency weighting • iOS measurement mode: audio processing is switched off so readings are not altered • Calibration wizard plus built-in offset profiles for ~30 iPhone models • Honest clipping detection warns you when the mic reaches its limit

PRO METRICS, COMPLETELY FREE • Noise dosimeter to NIOSH (85 dB, 3 dB) and OSHA (90 dB, 5 dB) standards • Live dose %, TWA and time-to-limit projection • Percentiles L10 / L50 / L90 / L95 • Time above threshold and a full dB histogram

SEE THE SOUND • FFT spectrum with peak frequency readout • Scrolling spectrogram (waterfall) • 31 third-octave bands with peak hold

DOCUMENT AND PROVE IT • Multi-page PDF report: chart, statistics, percentiles, dose and a threshold-exceedance table with start, end, duration and max • CSV and PNG export • Overnight and long-session recording with adaptive sampling, auto-stop timer and a quiet night preset • Session history with search, date and dB filters, tags, notes and markers • Trends dashboard: daily Leq, streaks, loudest day and hour

PRIVACY BY DESIGN Audio is analysed live and never recorded or stored. No accounts, no analytics, no trackers, no cloud. Everything stays on your iPhone. You can erase all data at any time from Settings.

ACCURACY NOTE NoiseLedger uses the built-in iPhone microphone, so readings are approximate and vary by device. It is a helpful indicator, not a certified instrument. For legal, workplace-compliance or safety-critical measurements, use a calibrated Class 1 or Class 2 sound level meter.