This decibel meter turns the microphone in your phone, laptop, webcam or USB headset into a sound level meter. It shows how loud it is in dBA, dBC or dBZ on an analog dial and a digital readout, keeps the minimum, maximum, average (Leq) and peak level, and draws a graph of the last 1, 5 or 15 minutes. It runs in Chrome, Edge, Firefox and Safari on Windows, Mac, ChromeOS, Android and iPhone. Sound is measured inside the browser tab and is never recorded or sent anywhere.
How to measure noise with the decibel meter
- Press Start measuring and allow the microphone when your browser asks. If you have more than one mic, pick it in Input.
- Hold the device still and point the mic at the sound. A phone's main mic is on its bottom edge. A laptop's mics sit near the webcam or above the keyboard.
- Keep A weighting and Fast response for everyday noise. Pick C for music, engines and other bass heavy noise, and Slow for a steadier number.
- Measure for at least 30 seconds, and for several minutes if the noise comes and goes. Read the Average (Leq) rather than the moving number.
- Press Copy results to save a summary, or CSV for a second by second log you can open in a spreadsheet.
Keep your hands, clothes and the phone case clear of the mic, and do not talk while you measure. Your own voice close to the mic will be the loudest thing in the room.
What the readings mean
| Reading | What it tells you | What to expect |
|---|---|---|
| Sound level now | The level right now, with your weighting and response | Moves with the sound |
| Min | The quietest moment, which is the background noise of the room | 30 to 40 dBA in a quiet room |
| Max | The loudest moment since you started | Depends on the event |
| Average (Leq) | The steady level with the same total energy over the whole time. Noise limits use this figure | Between Min and Max, usually closer to Max |
| Peak | The highest instant of the raw sound, unweighted | A few dB to 20 dB above Max for claps, slams and bangs |
| Daily limit | How long NIOSH says a person can spend at your dBA average each day | 8 hours at 85 dBA, 4 hours at 88 dBA |
Fast response follows the sound with a 0.125 second time constant and Slow with a 1 second one, the two settings sound level meters use. The CSV log gives one row per second with the A, C and Z average, the fast maximum and the peak.
Everyday sound levels
These average levels come from the CDC list of noise sources.
| Sound | Level |
|---|---|
| Soft whisper | 30 dB |
| Refrigerator hum | 40 dB |
| Normal conversation, air conditioner | 60 dB |
| Washing machine, dishwasher | 70 dB |
| City traffic heard inside a car, gas lawnmower, leaf blower | 80 to 85 dB |
| Motorcycle | 95 dB |
| Car horn at 5 m, approaching subway train, football or hockey crowd | 100 dB |
| Personal music player at full volume, rock concert | 105 to 110 dB |
| Standing beside a siren | 120 dB |
| Firecrackers | 140 to 150 dB |
How loud is too loud
NIOSH, the US institute for workplace safety, recommends no more than 85 dBA averaged over 8 hours, and halves the time for every 3 dB above that: 4 hours at 88 dBA, 2 hours at 91 dBA, 1 hour at 94 dBA and 15 minutes at 100 dBA. The legal limit for US employers, set by OSHA, is looser at 90 dBA for 8 hours. For music and other leisure noise, the World Health Organization counts listening time per week: 80 dB is safe for 40 hours a week, 90 dB for 4 hours and 100 dB for only 20 minutes.
If you have to raise your voice to talk to someone an arm's length away, the noise is probably above 85 dB. Leave, turn it down or wear hearing protection. Ringing ears or muffled hearing after a loud event is an early warning sign, and a hearing frequency test a day later shows whether the highest tones have come back.
Why a phone or laptop mic reads lower or higher
Built-in mics are made for voices, not measurement, so the same sound can read differently from one device to the next. The usual reasons, from the most common:
- No calibration. Your browser gives the level relative to the loudest sound the mic can take. The meter assumes a typical mic, which can put it several decibels out until you calibrate.
- Voice processing. Automatic gain lifts quiet sounds and turns down loud ones, and noise suppression removes steady noise such as fans. The meter turns all three switches off. If your browser keeps one on anyway, the panel says so.
- The input volume. Windows, macOS and Android let you change mic volume, and every change shifts the reading. Set it once and leave it.
- A floor in quiet rooms. Small mics have their own hiss, so many cannot read much below 30 to 40 dB. If Min never drops in a silent room, you have reached the mic's floor.
- Overload in loud places. Above roughly 100 to 120 dB many mics and sound chips clip. The meter warns you when that happens, because the real level is then higher than the reading.
- Bass. Tiny mics pick up deep bass weakly, so dBC and dBZ readings of subwoofers and engines can read low.
To check the mic itself, run a mic test first. If the level never moves at all, follow the steps for a mic not working.
Calibrate the meter against a real sound level meter
- Put this device and a real sound level meter side by side, with both mics pointing the same way.
- Play a steady sound at a moderate level, such as a fan, or pink noise from a speaker about a metre away.
- Set both to A weighting and wait a few seconds for the numbers to settle.
- Type what the real meter shows into A real meter reads and press Match. The meter sets the offset from its last 3 seconds.
The offset is saved for that microphone in this browser. Each mic gets its own offset, so a headset and a laptop mic keep separate settings. Calibrate again if you change the input volume in your system settings.
Classroom noise light
The Classroom light fills the screen with a traffic light that the class can see from the back of the room. It uses dBA with Slow response, waits half a second before turning red so one dropped book does not trigger it, and needs the room to stay quieter for a second and a half before it steps back down. The side panel shows how much of the lesson stayed green and how many times it went red.
Set the yellow and red levels in the panel under the meter before you open it. Normal conversation is about 60 dB, so yellow from 60 dB and red from 70 dB lets quiet talk through and catches shouting. Put the laptop where it hears the room, not next to the teacher's desk, and press Esc to leave.
Using it as a noise meter or db meter at home and work
For a neighbour or traffic problem, measure for 5 to 15 minutes at the time the noise happens, from the room where it bothers you, with windows as they normally are. Write down the time with the Leq and Max, or keep the CSV. For a home studio or a home theater, use C weighting and the frequency analyzer to see which frequencies are loud, since bass problems hide in dBA readings.
What an online sound level meter cannot do
A browser meter is not a certified Class 1 or Class 2 instrument under IEC 61672, and no website can make a phone mic into one. It cannot measure sound the mic does not hear well, such as deep bass below about 30 Hz or ultrasound, and its peak reading is the highest digital sample rather than a true analog peak. For workplace assessments, use a Class 2 meter or a personal noise dosimeter. On an iPhone, the free NIOSH Sound Level Meter app paired with a calibrated external mic is a cheaper step up.
Decibel meter questions
How accurate is an online decibel meter?
Uncalibrated, treat the number as an estimate. Your browser reports the level relative to the loudest sound the mic can take, not in real decibels, so the meter assumes a typical microphone and can be several decibels off, sometimes 10 dB or more. Match it once to a real sound level meter with Calibration and it tracks steady noise closely on that microphone, as long as you leave the input volume alone.
How many decibels is too loud?
NIOSH sets 85 dBA averaged over 8 hours as the limit for a working day, and every 3 dB more halves the safe time: 88 dBA for 4 hours, 91 dBA for 2 hours, 100 dBA for 15 minutes. The CDC says long exposure above 70 dB may start to damage hearing. The Daily limit readout applies the NIOSH rule to your average.
What is the difference between dBA and dBC?
dBA uses A weighting, which turns down low and very high frequencies the way your ears do at everyday levels. It is the figure hearing limits and most noise rules use. dBC is close to flat and keeps the bass, so music, engines and fans read higher in dBC than in dBA. A big gap between the two tells you the noise is mostly bass.
How loud should a classroom be?
The World Health Organization advises background noise of no more than 35 dB in a classroom during lessons, so speech stays easy to follow. Activity is louder than that: normal conversation is about 60 dB. The classroom light starts at yellow from 60 dB and red from 70 dB, and you can change both.
Can I use this decibel meter for a noise complaint?
It is good for a diary. Measure each event for a few minutes, then press Copy results or CSV to keep the time, the average (Leq) and the loudest level. Formal action usually depends on readings from a calibrated Class 1 or Class 2 meter, so treat these figures as supporting evidence.
Why does my phone app show a different number?
Apps and websites use different calibrations, weightings and response times, and your phone may apply its own noise processing to one but not the other. Compare them with the same weighting (A) and response (Fast), side by side, on steady noise. Calibrate this meter to whichever one you trust more.
Does the decibel meter record what I say?
No. The meter reads the loudness of the sound many times a second inside this browser tab and keeps only the numbers. No audio is recorded, stored or sent anywhere, and the microphone turns off when you press Stop or leave the page.