How accurate is an online decibel meter?
It gives a useful estimate, not an exact measurement. Every microphone has its own sensitivity, and phones and laptops filter sound before the browser receives it. We switch off echo cancellation, noise suppression and automatic gain to get the rawest signal, and apply a filter that roughly follows how the ear hears (similar to A-weighting). Expect the reading to be within about 5 to 10 dB of a real sound level meter in normal rooms.
If you have a real meter or a known reference, use the calibration slider to line the two up. For anything official, like a noise complaint or a workplace check, use a calibrated sound level meter.
Common sound levels
| Level | Example |
|---|---|
| 30 dB | Whisper, quiet library |
| 40 dB | Quiet room at night |
| 60 dB | Normal conversation |
| 70 dB | Busy traffic, vacuum cleaner |
| 85 dB | Heavy traffic, food blender. A common limit for 8 hours of exposure at work |
| 100 dB | Motorbike, loud music through headphones |
| 110 to 120 dB | Rock concert, siren up close |
The decibel scale is logarithmic. Every 10 dB step sounds roughly twice as loud, and every 3 dB step doubles the sound energy. Long exposure above 85 dB can damage hearing, so use ear protection at concerts and with loud tools.
Tips for a better reading
- Hold the phone with the microphone pointing at the sound, and keep your fingers off it.
- Stay still. Handling noise shows up as spikes.
- Measure for at least 30 seconds and use the average, not a single peak.
- Wind ruins outdoor readings. Shield the mic or measure indoors.
Frequently asked questions
Short answers to the questions people ask most about this test.
Can my phone measure decibels?
Yes, as an estimate. Phone microphones are designed for speech, so very quiet and very loud sounds are less accurate. Readings in the 40 to 90 dB range are the most reliable.
Is the sound recorded?
No. The page only measures the level on your device. No audio is stored or uploaded.
What does dB mean?
A decibel (dB) is a unit for loudness on a logarithmic scale. 0 dB is roughly the quietest sound a young person can hear, and 120 dB is painfully loud.
Why does the meter never go below 30 dB?
Microphones and the electronics behind them have their own noise floor. In a very quiet room the meter shows that floor rather than true silence.