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Decibel Sound Meter

How to measure decibels on your iPhone

Open Decibel Sound Meter, allow the microphone and read the live number on the Meter tab. For a figure you can rely on more than a single instant, tap Start Recording for 30 to 60 seconds and read AVG, the energy average of that period.

4 min read · Updated 2026-09-17

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Can I measure decibels with my iPhone?

Yes. The iPhone's microphone hears the sound around you just fine for everyday use — a blender, a crowded bar, a neighbour's generator. A sound meter app turns that signal into decibels. Decibel Sound Meter applies the A-weighting curve described in IEC 61672, which shapes the reading to how human ears hear, and a Fast (125 ms) response, so the number follows the sound without jittering on every sample.

Phone microphones read low, so out of the box the app adds a starting offset: +10 dB on iPhone and +8 dB on iPad. Treat the result as a good estimate, not a certified reading — it won't catch a sudden bang accurately, and it drifts a little between phone models. If you need it closer to a reference meter, calibrate it once (there is a separate guide for that).

How to check decibels on iPhone, step by step

  1. Open the app. On the Meter tab, titled Sound Meter, allow microphone access when asked. The reading starts on its own.
  2. Hold the phone still at the spot you want to measure, microphone uncovered, and keep your hands and voice away from it.
  3. Read the big number (the current level), the peak shown under it and the word that describes the level, such as Quiet or Loud.
  4. For a stable figure, tap Start Recording. MIN, AVG and MAX start filling in and the SOUND LEVEL HISTORY chart shows the Last 60s.
  5. After 30 to 60 seconds, tap Stop Recording and choose Stop & Save. Recordings of 10 seconds or less are saved without asking.
  6. The Export Report sheet opens; close it if you don't need a report now. Tap the clock button to open History, then tap the session for Measurement Details, where you can add Notes and Tags.

What do the numbers on the meter mean?

What the Meter tab shows
On screenWhat it tells you
Big numberThe current A-weighted level in whole decibels, updated continuously
PeakThe highest recent level, held for 2 seconds so you can read it
MINThe quietest moment of the recording
AVGThe energy average (LAeq) of the recording, not a simple mean
MAXThe loudest moment of the recording

Why an energy average? Decibels are logarithmic, so loud moments carry far more energy than quiet ones. Thirty minutes at 70 dB followed by thirty minutes at 90 dB average to 87.0 dB, not 80 dB. That matches what reaches your ears.

How to measure decibels in a room or at home

A single glance tells you little, because a room changes second by second. Record instead, and compare like with like: same spot, same time of day, same distance from the source.

Example checks at home
What you want to knowHow to measure itWhat to read
How quiet is my bedroom at night?Record 60 seconds from the pillow, with doors and windows as they are when you sleepAVG and MAX
How loud is the white noise machine at the crib?Put the phone where the baby's head lies, machine at its usual volume, record 60 secondsAVG
Is the TV too loud?Record from your seat during normal viewingAVG, then compare with Normal Conversation in Noise Levels
Which room is quietest for working?Record 60 seconds in each room at the same time of dayCompare the sessions in History

Tips for a reading you can trust

  • Record at least 30 to 60 seconds; one instant can be a door slam or a cough.
  • Stay quiet while measuring. Your own voice is the loudest thing near the microphone.
  • Take the phone out of your pocket, and don't let a thick case or your fingers cover the microphone.
  • If the display shows --, the meter is stopped or a phone call has taken the microphone; it resumes on its own.
  • Open Noise Levels with the list button to compare your number with everyday sounds, from a Quiet Library at 40 dB to a Subway Train at 100 dB.
  • Calibrate if you need the absolute number rather than comparisons between places.

Questions and answers

Can I measure decibels on my iPad?
Yes. Decibel Sound Meter runs on iPad with iOS 17 or later and works the same way as on iPhone. Out of the box it adds +8 dB on iPad instead of +10 dB, so calibrate the iPad on its own if you want to compare it with a phone.
How do I measure decibels on iPhone for free?
Download Decibel Sound Meter; the live meter, recordings with minimum, average and maximum, history and calibration are free. The free version shows ads, and some exports need Premium or a short ad.
How long should I record?
Thirty to sixty seconds for a steady sound such as a fan, a room or a machine. For something that comes and goes, like traffic or music, record the whole episode. History keeps your last 100 recordings.
Why is AVG higher than the level I saw most of the time?
Because it is an energy average. A few loud seconds add much more energy than many quiet ones, so they pull the average up. That is how sound professionals average noise too.

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