Decibel meter on your phone: measuring dB on iPhone and Android

Can a phone really measure decibels?

Yes, within limits. Every phone has a microphone that turns air pressure into a signal, and a sound meter app converts that signal into decibels. Most apps show A-weighted dB (dBA), the scale used for noise and hearing, which gives less weight to low rumble than to the midrange your ears are most sensitive to.

iPhone has no built-in decibel meter app. The Hearing control in Control Centre shows how loud your headphone audio is, not how loud the room is. On Apple devices, room noise is measured by the Noise app on Apple Watch. On an iPhone without a watch, or on any Android phone, you need a sound meter app.

How to measure decibels with your phone, step by step

The same routine works in any meter app. The aim is to give the microphone a clear, steady view of the sound and to read an average rather than a single spike.

Find the main microphone. On most phones it sits on the bottom edge, next to the charging port. Don't cover it with a finger or a bulky case.
Hold the phone at arm's length or rest it on a stable surface, microphone pointing toward the source. Hands and pockets muffle the reading.
Keep quiet yourself. Talking, breathing on the phone or tapping the screen all show up in the number.
Measure for 30 to 60 seconds and note the average and the maximum, not the first value you see.
Avoid wind and direct airflow from fans or vents. Moving air hits the microphone and adds rumble that is not real noise.
To compare two places or two times of day, measure from the same spot and at the same height each time.

Using the dB meter in Wring

Wring has a dB meter alongside its water eject, dust cleaning, speaker test and tone generator tools. It reads the microphone and shows the sound level in decibels, so you can follow the steps above without any extra gear. The app asks for microphone access the first time you open the meter.

The meter has an optional camera measurement mode. Point the camera at the scene, tap the shutter, and Wring takes a photo with the decibel reading drawn on it. The photo is created on the phone and is not uploaded: you save it or tap Share yourself. It is handy when you want a record of how loud a bar, a workshop or a neighbour's party was, with the place in the picture.

Camera access is requested the first time you open camera mode. On iPhone and iPad, Wring only asks to add photos and never sees your existing library. On Android the photo goes to Pictures/Wring.

Wring is free with ads and some limits; Pro removes both. Download it from the App Store for iPhone and iPad or from Google Play for Android.

How accurate is a phone decibel meter?

More accurate than most people expect, provided the app is good. NIOSH, the US workplace safety institute, examined 192 sound meter apps and found only a handful that met its accuracy criteria. Its own NIOSH Sound Level Meter app for iOS stays within about 2 dBA of a professional reference meter when it uses the iPhone's built-in microphone.

Android is harder to pin down. Microphones and audio processing differ from one manufacturer to the next, which is why NIOSH did not release an Android version. Treat Android readings as a good relative measure: louder or quieter, better or worse after a change.

For better accuracy NIOSH recommends an external microphone that can be calibrated with an acoustic calibrator. Even then, NIOSH says a phone app does not replace a professional sound level meter or a noise dosimeter, and it is not meant for compliance measurements.

What the numbers mean: 80, 85 and 95 dB

Decibels are logarithmic. A rise of 3 dB roughly doubles the sound energy, so as far as hearing risk goes, 88 dB is not slightly louder than 85 dB: it is twice the dose. That is why, in NIOSH's guidance, the safe listening time halves with every 3 dB step.

Use these reference points from public health bodies to make sense of a reading.

85 dBA is the NIOSH recommended limit for an 8-hour workday. At this level you usually have to raise your voice to talk to someone about a metre away. Lawn mowers, vacuums and many power tools sit around 85 to 90 dBA.
Each extra 3 dBA halves the safe exposure time, according to NIOSH.
95 dBA and above: you have to shout to be heard a metre away. Bars, nightclubs, chainsaws and big sports events are typical examples.
Apple's Noise app guidance: about 80 dB for around 5.5 hours a day, or about 90 dB for around 30 minutes, can cause temporary hearing loss.
The WHO-ITU safe listening standard for personal audio uses 80 dB for 40 hours a week as the reference for adults.

What not to do

A meter app is a tool for understanding noise. A few habits lead to wrong numbers or wrong conclusions.

Don't hold the phone right up against a speaker, an engine or an exhaust to get a big number. Measure where people actually stand or sit.
Don't rely on a single reading. One slammed door or one shout says little about the overall level.
Don't treat a phone reading as proof that a workplace or legal limit has been broken. Compliance needs a calibrated instrument and a proper method.
Don't use the meter to judge your own hearing. A dB reading measures the sound around you, not what your ears can still hear.
Don't leave the microphone half covered by a case, a pocket or lint in the grille.

When to use a professional meter or see a specialist

Use a calibrated sound level meter, or ask an acoustics professional, when the number has consequences: workplace noise assessments, disputes with neighbours or landlords that may end in a formal complaint, or checking that a venue meets a local limit. A phone reading is still useful for deciding whether that step is worth taking.

See a doctor or an audiologist if you notice ringing in your ears, muffled hearing after loud events or trouble following conversations. A decibel meter can tell you that a place is loud, but it cannot diagnose hearing damage.

Quick answers

Short answers to the questions people search for most about phone decibel meters.

Does iPhone have a built-in decibel meter? Not for room noise. The Hearing control in Control Centre shows headphone audio levels. For room noise you need the Noise app on Apple Watch or a sound meter app.
Is a decibel meter app accurate? A well-made app on iPhone can get within about 2 dBA of a reference meter. Android varies by model. Use it as an estimate.
How loud is too loud? In NIOSH's guidance, hearing risk starts with long exposure at 85 dBA and above, and the safe time halves with every 3 dB.
Why does my reading jump around? Sound changes all the time. Read the average over 30 to 60 seconds rather than the live number.
Can I use the reading for a noise complaint? As a personal record, yes, and a dated photo from camera mode helps. For a formal case, ask which measurement the authority accepts.
My readings seem low. Is the microphone blocked? Lint in the bottom grille can muffle sound. Our guide on how to clean a phone speaker shows how to brush grilles safely, and the free online speaker test checks the speaker side.