Sound Level Meter: Decibel
SonoMeter: Decibel Meter
A, C and Z weighting, third-octave analysis, LAeq and an A4 PDF report in one tap. Built to the IEC 61672-1 standard.
Download on the App StoreFree on the App Store, with in-app purchases. Requires iOS 16 or later. Rated 4.9 out of 5 (8 ratings).
What Sound Level Meter: Decibel does
A, C and Z weighting
Real cascaded biquad filters, switchable on the fly — not simple high-pass/low-pass approximations.
1/3 octave analysis
Frequency analysis and several live visualisations: histogram, gauge, dial, timeline graph.
Every metric
LAeq, min, max, average, peak, with Fast (125 ms), Slow (1 s) and Impulse time integrations.
A4 PDF report
Every recorded session produces a PDF with statistics, timeline, location and notes. Print it or send it.
Accuracy and calibration
The app implements the IEC 61672-1 specification: A and C weighting through cascaded filters, exponential averaging on squared pressure — the correct method — and calibration specific to the iPhone model in use.
After a one-off calibration against a known reference, expect 2 to 3 dB typical accuracy between 40 and 95 dB. The measurable ceiling is limited by iPhone hardware, around 104–110 dB.
What it replaces, and what it does not
For monitoring, awareness and personal documentation it does the job: documenting a neighbour's noise, setting up a studio, watching your own exposure, running a pre-check before a formal survey.
For a legally admissible acoustic measurement, a certified class 1 or 2 meter remains the reference. The app does not substitute for one and does not claim to.
Your measurements stay with you
No ads, no subscription. Sessions are stored locally on the iPhone and nothing is uploaded: your acoustic data stays yours.
Sound Level Meter: Decibel in pictures
Frequently asked questions
What is the real accuracy?
2 to 3 dB between 40 and 95 dB after calibrating against a known reference. The iPhone hardware ceiling is around 104 to 110 dB.
Does it replace a certified meter?
Not for a legally admissible measurement: a class 1 or 2 instrument is still required. Yes for monitoring, awareness and personal documentation.
Why does another app show a different value?
Microphone sensitivity varies by iPhone model and every app handles calibration differently. Use the built-in calibration screen to align with a reference you trust.
Can I export my measurements?
Yes, every recorded session generates a complete A4 PDF to print, email or share over AirDrop.
How is my data handled?
Sessions stay stored locally on your device. Nothing is uploaded.