Decibel Meter
Measure sound with your phone or laptop microphone. See a live level, min, max, average and Leq, and a 60-second chart. The decibel figure stays uncalibrated until you match the offset to a real meter, and it is not a legal or workplace reading. Nothing is recorded.
Not dB SPL. This figure is dBFS plus a default offset of 94. Not a legal or workplace reading.
Fast follows claps and speech. Slow smooths the reading for steady noise like traffic or a fan.
Compare with a real meter or a phone app you trust, then move this until the numbers match. The result is only as good as this offset. Saved on this device.
- 20 dBRustling leaves
- 30 dBWhisper, quiet library
- 40 dBQuiet room, fridge hum
- 60 dBNormal conversation
- 70 dBVacuum cleaner, busy office
- 80 dBCity traffic, alarm clock
- 85 dBNIOSH 8-hour guide (dBA)
- 95 dBMotorbike, subway train
- 100 dBConcert, nightclub
- 110 dBFront row of a rock show
- 120 dBThunder, siren up close
Private by design: the audio is analysed in your browser and never leaves your device. Nothing is recorded or uploaded, and the microphone is released when you press Stop or leave the page.
dBFS is the digital level the microphone delivers, relative to full scale. The big number adds your offset and is not a measured dB SPL. There is no A-weighting. Phone and laptop mics are not calibrated. They may still apply gain and clip on very loud sound, so treat the figure as a guide, roughly plus or minus 5 to 10 dB, until you set the offset. It is not a legal or workplace reading.
Can your phone really measure decibels?
What a decibel is
Decibels are a log scale, so the numbers do not add up the way you expect. Every +3 dB doubles the sound energy, and every +10 dB sounds roughly twice as loud to your ears. That makes 80 dB traffic about four times as loud as a 60 dB conversation, and carrying 100 times the energy. This meter takes the RMS of the microphone signal 20 times a second, smooths it with a 125 ms (fast) or 1 s (slow) time weighting, and shows Leq, the energy average over the session. Noise rules use that kind of average on a calibrated A-weighted meter, which this is not.
How much is too much
NIOSH recommends no more than 85 dBA averaged over 8 hours, and halves the safe time for every 3 dB above that: 4 hours at 88 dBA, 1 hour at 94 dBA, about 15 minutes at 100 dBA and under 2 minutes at 110 dBA. That is a general reference for a real A-weighted meter. This page is unweighted and, until you set an offset, uncalibrated, so it does not measure that dose. A concert or club can pass that limit in one evening. If you are often in loud places, a quick hearing test is worth doing.
Why decibel meter apps are estimates
A real sound level meter has a calibrated microphone and a known sensitivity. Your phone or laptop does not. Browsers let us switch off echo cancelling, noise suppression and auto gain, but some devices ignore that, and built-in mics roll off the bass and clip above about 100 to 110 dB. So any decibel meter app that shows a precise dB SPL number without calibration is guessing, and so is this one, which is why it also shows the raw dBFS value and lets you set the offset. The number is only as good as that offset, and it is not a legal or workplace reading. Two phones can disagree by 10 dB in the same room.
Tips for a better reading
Calibrate once against a trusted meter, then keep using the same device and browser. Hold the mic toward the sound, keep fingers and cases off it, and stay still: handling noise and wind both read as loud. Use slow response and watch Leq for steady noise, fast and max for short events. For a repeatable test sound, play a steady tone from the tone generator, and start it quiet.
Related tools
Check your ears with the hearing test, your speakers with the sound test and your left and right channels with the headphone test, or make a test signal with the tone generator.
Frequently asked questions
Is this a real dB SPL meter?
No. An AnalyserNode reads float samples from the microphone 20 times a second. The page takes the mean square (RMS squared) and turns it into dBFS with 10 log10. The big number is that dBFS value plus an offset, and anything below 0 is shown as 0. Until you set the offset against a real meter, it is an uncalibrated estimate, not dB SPL, and not a legal or workplace reading. The smaller figure under it is the raw dBFS level. There is no A-weighting filter, so it is not dBA either.
What does the calibration offset change?
Shown dB equals dBFS plus the offset, with results below 0 shown as 0. The slider runs from 60 to 130 and starts at 94, which only maps digital full scale to 94 on the display. Compare it with a meter you trust, on the same phone or laptop and the same browser, then move the slider until they agree. The number is only as good as that offset. Reset puts it back to 94. The value is saved in this browser and is not uploaded.
What if I block the microphone?
Start calls getUserMedia. If you deny permission, or the system blocks the browser, the page shows Microphone access was blocked and how to allow it in the address bar, on iPhone or iPad, on Android and on a Mac. The meter does not keep running. A missing microphone, a browser that cannot open one here, and a mic another app is using each get their own message.
Does the audio leave my device?
No. Samples stay in this tab for the level math. Nothing is recorded and nothing is uploaded. Stop stops every track on the stream and closes the audio context, which turns the microphone indicator off. Leaving the page does the same.
What are Fast, Slow, Leq and Peak?
Fast and Slow smooth the mean square with time constants of 125 ms and 1 second. They are not frequency weightings. Leq is the energy average of the raw mean square for this session. The first 0.6 seconds are skipped, and counting pauses while the tab is hidden. Peak is the loudest sample in that same stretch, shown on the same offset scale. Min and max use the time-smoothed level. Average is the plain mean of those dB readings, not a second Leq.
Can I use the safe-time line at work?
No. The loudness list and the NIOSH note (85 dBA over 8 hours, with the time cut in half every 3 dB) are a general reference for a real A-weighted sound level meter. This page is unweighted. Unless you have set an offset, it is also uncalibrated, and even then the number is only as good as that offset. The session line is an illustration, not a noise dose and not a legal or workplace reading.
Why might two devices disagree?
Built-in mics are not lab microphones. The page asks the browser to turn off echo cancellation, noise suppression and auto gain, but some phones and laptops ignore that. Bass can be rolled off, and very loud sound can clip. Wind and fingers on the mic both look loud. Use one device, point the mic at the sound, and set the offset once. Use Slow and Leq for a steady fan or for traffic, and Fast and Max for a short noise.