How the decibel meter works
Press start and allow your microphone. The meter reads the sound reaching the mic many times a second and turns it into a level in decibels. It shows the level right now, the loudest moment since you started (peak), the average, and a line of the last minute. Your audio stays on your device: nothing is recorded, uploaded or saved.
- Now is smoothed over about an eighth of a second, like the fast setting on a sound level meter, so it follows speech and short sounds without flickering.
- Peak is the highest smoothed level since you started or last reset.
- Average is an energy average: loud moments count for more than a simple average of the numbers would give them, which is how noise levels are usually averaged.
The meter asks the browser to switch off noise suppression and automatic gain, which would otherwise change the level on their own. Some browsers and phones keep them on anyway.
Why the reading is approximate
A real sound level meter has a calibrated microphone: its makers know exactly which signal equals which sound level. A phone, laptop or headset mic has no such calibration, and models differ a lot. So this tool starts from a middle-of-the-road guess and labels every number dB (approximate, uncalibrated). It is good for comparing: louder or quieter than yesterday, this room against that one, before and after you close a window. It is not a measurement to rely on for work safety, legal or medical purposes.
The readings are also unweighted. Professional meters usually apply A-weighting (dBA), which counts low and very high sounds less, the way our ears do. Deep sounds like traffic rumble can therefore read higher here than on a dBA meter.
Calibrating with an offset
If you have access to a calibrated sound level meter, you can bring this one close. Put both side by side, play a steady sound such as pink noise or a fan, and type what the reference meter shows into the box. Press Match and the offset is set so the two agree. You can also raise or lower the offset 1 dB at a time. The offset is saved in this browser for this device only; a different phone or mic needs its own.
Typical sound levels
The table in the tool lists rounded, commonly quoted levels as a rough guide: a whisper around 30 dB, normal conversation around 60, heavy city traffic around 85, a loud concert over 100. Real levels depend on how far away you are and on the source itself. Health agencies such as the US National Institute for Occupational Safety and Health (NIOSH) recommend limiting exposure to noise above 85 dBA averaged over an eight-hour day, and far less time at higher levels. If your surroundings often read near or above that here, it's worth checking with a proper meter.
Questions
Is a phone decibel meter accurate?
Not on its own. Without calibration, readings can be several decibels off or more, and it varies by phone and mic. For comparisons in the same place with the same device, it's useful.
Why does the meter read low in a loud place?
Phone and laptop mics, and the processing around them, often hold loud sounds back, so readings near the top of the scale are the least reliable. A calibration offset set in a quieter place can also drift at very high levels.
Why doesn't it read zero in a quiet room?
Every mic and its electronics make a little noise of their own, which sets the lowest reading. Cheap mics have a higher floor, so very quiet rooms read louder than they are.
Does it record me?
No. The level is worked out in your browser frame by frame; no audio is stored or sent anywhere. Press Stop and the microphone switches off.
Checking how your own mic sounds? The mic test records a clip you can play back. For a noisy room, a dynamic mic picks up less of it: see our best dynamic microphones or the microphone finder.