How to use
- Click Start and allow the browser to use the microphone.
- Place the device where you want to measure, keep the microphone uncovered and watch the current level and the last 30 seconds.
- If you have a calibrated meter, compare the two and adjust the offset under Calibration.
Options explained
- Average (Leq)
- The equivalent continuous level, averaged by sound energy rather than by adding up decibel numbers — the same method as professional meters.
- Offset
- Browsers report levels relative to full scale (dBFS). By default full scale is taken as 100 dB; microphone sensitivity varies a lot between devices.
How the number is calculated
The browser gives the tool the microphone signal as sample values between −1 and 1. The level shown is:
dB = 20 × log10(RMS of the samples) + offset (never below 0)With the default offset of 100, a signal whose RMS is 0.01 (−40 dBFS) shows as 60 dB. To calibrate, measure the same sound with a reference meter and change the offset by the difference. If the reference reads 70 dB and this page reads 63 dB, raise the offset from 100 to 107.
Why Leq is not a simple average
Decibels are logarithmic, so the average is taken on energy: Leq = 10 × log10(mean of 10^(dB ÷ 10)). Half a minute at 60 dB and half a minute at 80 dB gives 77.0 dB, not 70 dB, because the louder part carries 100 times the energy. Every 3 dB doubles the sound energy.
Frequently asked questions
How accurate is it?
Only roughly. Phone and computer microphones are uncalibrated and their frequency response is not flat, so readings are often several dB off. Complaints, legal cases and workplace assessments need a certified sound level meter.
Why does the reading barely move?
Some browsers or systems force automatic gain control and noise suppression. This page asks for them to be turned off, but some devices ignore that — try another browser.
Does it record?
No. The level is calculated live in your browser; no audio is stored or uploaded.
Privacy
This tool runs entirely in your browser. Your files and text are processed on your device and are never uploaded to our servers.