🔈 Decibel Meter
Measure sound level with your microphone: live dB(A) estimate, min, max and average, a level graph and noise chart. Calibrate for better accuracy.
Calibrate with a known reference
Place your device next to a calibrated sound level meter (or a meter app you trust), play a steady sound, and enter the meter’s reading while measuring. The offset is saved on this device.
Current offset: 100.0 dB (default guess).
Typical sound levels
| 30 dB | Whisper, quiet library |
|---|---|
| 40 dB | Quiet room, refrigerator hum |
| 60 dB | Normal conversation |
| 70 dB | Vacuum cleaner, busy restaurant |
| 85 dB | Heavy city traffic — prolonged exposure risks hearing damage |
| 100 dB | Motorcycle, power tools |
| 110 dB | Rock concert, car horn nearby |
| 120 dB | Thunderclap, siren up close — pain threshold |
What Decibel Meter Does
This decibel meter uses your device’s microphone to show the sound level around you, live, with the minimum, maximum and average (Leq) since you started, a scrolling graph, and a chart of typical sound levels for comparison. An approximate A-weighting filter makes readings follow how people perceive loudness, the same weighting used for most noise limits and hearing guidelines.
The browser’s voice processing — noise suppression, automatic gain and echo cancellation — is switched off for measurement, because it would silently squash loud sounds and boost quiet ones. Even so, phone and laptop microphones are not calibrated instruments, so the absolute number is an estimate until you calibrate against a known reference. Changes in level, and comparisons between places measured with the same device, are far more trustworthy.
How to Use Decibel Meter
- Press Start and allow microphone access
- Hold the device still, microphone pointing toward the sound
- Read the live level, plus minimum, maximum and average
- Compare with the typical sound levels chart
- Calibrate against a reference meter for better accuracy
Formula Used by Decibel Meter
From microphone signal to decibels
dBFS = 20 × log₁₀(RMS amplitude) · estimated dB = dBFS + calibration offset
Worked example
An RMS level of 0.01 with an offset of 100 dB.
- 20 × log₁₀(0.01) = −40 dBFS
- −40 + 100
Result: About 60 dB — normal conversation level.
Average level (Leq)
Leq = 10 × log₁₀(average of 10^(L/10))
Worked example
Half the time at 60 dB, half at 80 dB.
- Average of 10⁶ and 10⁸ = 5.05 × 10⁷
- 10 × log₁₀(5.05 × 10⁷)
Result: About 77 dB — loud periods dominate an energy average.
Decibels and Loudness
| Change | Sound energy | How it sounds |
|---|---|---|
| +3 dB | 2 × | Just noticeably louder |
| +10 dB | 10 × | About twice as loud |
| +20 dB | 100 × | About four times as loud |
How to Read Your Result
Protecting your hearing
Hearing damage depends on level and time together. Guidelines commonly treat about 85 dB(A) over a working day as the point where hearing protection becomes important, and every 3 dB increase halves the safe time in the widely used equal-energy approach. If you have to raise your voice to be heard at arm’s length, it is probably loud enough to matter.
Getting consistent readings
Hold the device still, point the microphone toward the sound, and keep hands and cases away from it. Wind across the microphone reads as loud noise outdoors. For comparing rooms or times of day, use the same device and position each time.
Limitations & Accuracy Notes
- Not a certified sound level meter; do not rely on it for legal, workplace-compliance or medical measurements.
- Built-in microphones and their electronics limit accuracy at very low and very high levels, and some devices keep their own processing even when asked to turn it off.
- The A-weighting filter is an approximation of the standard curve.