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Noise Logger
Noise Logger
Sound level monitoring · iOS 17+
Leave it running overnight. Noise Logger listens continuously, captures every sound that crosses your threshold, and hands you a timestamped report you can hand to someone else.
What it does
Every feature exists because someone needed evidence and had nothing but a phone in their pocket.
Background monitoring survives screen lock. Start a session in the evening, read the report in the morning — no babysitting.
All nightSet a dB threshold and it captures the clip. A configurable hangover keeps one event as one recording instead of fragmenting it into thirty.
Threshold + hangoverA rolling half-second buffer is prepended to every clip, so the bang that triggered the recording is actually in the recording.
0.5 s bufferLevel triggers catch loud events. Frequency-band and single-tone triggers catch the specific ones — a compressor hum, an alarm, a resonance.
Band + single toneGPS coordinates, reverse-geocoded address, peak and average level, duration, trigger reason, and an optional photo at the moment of capture.
GPS + photoImport a microphone calibration file for per-frequency correction, or use the live calibrator screen with an acoustic calibrator to set your offset.
External mic readyWhy anyone should believe you
Every exported report ends with an integrity certificate: a SHA-256 digest of each audio clip and of the report itself. Change one byte and the digest no longer matches.
Measurement
Weighting curves and time constants follow IEC 61672. Energy averaging is true Leq, not an arithmetic mean of decibels.
An honest limitation. Noise Logger is a monitoring and logging tool, not a certified Type 1 or Type 2 sound level meter. iPhone microphones are tuned for voice. Treat readings as indicative, calibrate against a reference meter, and use a certified instrument where the law requires one.
| Frequency weighting | A · C · Z |
| Time weighting | Fast 125 ms · Slow 1 s |
| Averaging | Leq, energy-based |
| Peak detection | True sample peak |
| FFT sizes | 256 – 8192 points |
| Window functions | 8 selectable |
| Spectrum range | 0 – 20 kHz |
| Display modes | Bars · Lines · Waterfall |
| Pre-trigger buffer | 0.5 seconds |
| Export | PDF · PDF + audio ZIP |
| Data handling | On device only |
Start tonight
One session is usually enough to turn "it's too loud" into something with timestamps on it.