Sound Level Meter
Check how loud it is around you using your device's microphone. See the current level, minimum, average and maximum, a 60-second history graph and how it compares to everyday sounds. Readings are estimates, not a calibrated meter.
Estimate, not a calibrated meter
Browser microphones are not calibrated and may apply automatic gain, so treat readings as a rough guide (often ±10 dB). Current offset: 94 dB.
How to use the Sound Level Meter
- Press Start and allow microphone access when your browser asks.
- Watch the current level, the min, average and max, and the history graph.
- Choose Fast or Slow response: Fast follows quick changes, Slow gives a steadier reading.
- Calibrate if you can: adjust the offset, or play a sound of known level and press Calibrate.
- Press Stop to pause and Reset to clear the statistics and graph.
How the meter turns your microphone signal into decibels
The browser delivers the microphone signal as numbers between −1 and +1. The meter squares every sample, averages them with an exponential time weighting (125 ms for Fast, 1 s for Slow, the same time constants used by standard sound level meters) and converts the result to decibels relative to full scale:
dBFS = 10 × log₁₀(mean square) and estimated dB SPL = dBFS + calibration offset
Example: a mean square of 0.0001 (an RMS of 0.01) is 10 × log₁₀(0.0001) = −40 dBFS. With the default offset of 94 dB, the meter shows 54 dB. If a calibrated meter next to your phone shows 60 dB for the same sound, enter 60 and press Calibrate: the offset becomes 100 dB.
No frequency weighting (A or C) is applied, so low rumble counts fully. Professional meters usually show dB(A), which reduces bass, so this meter can read higher than a dB(A) meter in noisy, bass-heavy places.
Safe listening time by noise level
The NIOSH recommended exposure limit is 85 dB(A) averaged over 8 hours, with a 3 dB exchange rate: every 3 dB increase halves the safe time.
| Level | Maximum daily exposure (NIOSH) | Example |
|---|---|---|
| 85 dB | 8 hours | Heavy city traffic, food blender |
| 88 dB | 4 hours | Subway train |
| 91 dB | 2 hours | Lawn mower |
| 94 dB | 1 hour | Motorcycle |
| 97 dB | 30 minutes | Power tools |
| 100 dB | 15 minutes | Nightclub, hand drill |
| 110 dB | about 1.5 minutes | Rock concert |
Tips for better readings
- Hold the device still and point the microphone at the sound source; do not cover it with your hand or a case.
- Use Slow response for steady noise such as traffic or fans, and Fast for speech, music or sudden sounds.
- Very loud sounds (above roughly 100–110 dB) can overload small microphones, so the meter may read too low.
- Readings differ between devices. Calibrate once per device against a real sound level meter if you need comparable numbers.
- Use the Avg (Leq) value to describe a period of fluctuating noise, for example a 10-minute measurement of a noisy street.
Frequently asked questions
How accurate is an online decibel meter?
It is an estimate. Phone and laptop microphones are not calibrated, their sensitivity differs between models, and many apply automatic gain or noise suppression. Without calibration, readings can be off by 10 dB or more. Use it to compare levels and spot trends, not for legal or safety measurements, which need a certified Class 1 or Class 2 sound level meter.
How do I calibrate the meter?
Place your device next to a calibrated sound level meter, or use a reference sound of known level, type that level into the calibration box and press Calibrate. The tool sets the offset so the current reading matches. You can also adjust the offset manually. The setting is remembered in this browser.
What is the difference between dBFS and dB SPL?
dBFS (decibels relative to full scale) describes the digital signal level, where 0 dBFS is the loudest value the microphone input can represent. dB SPL (sound pressure level) is the physical loudness of sound in air relative to 20 micropascals. The meter converts dBFS to an estimated dB SPL by adding the calibration offset.
What noise level is harmful?
Long exposure above about 85 dB can damage hearing. Under the NIOSH recommendation, 85 dB is acceptable for 8 hours a day, and every 3 dB increase halves the safe time, so 100 dB is limited to about 15 minutes. Sounds above roughly 120 dB can be painful and cause damage almost instantly.
What do Min, Avg and Max mean?
Min and Max are the lowest and highest levels measured since you pressed Start or Reset. Avg is the equivalent continuous level (Leq), the energy average, which is what noise regulations usually refer to. It is higher than a simple arithmetic mean when the level fluctuates.
Does this tool record or upload my audio?
No. The microphone signal is analysed in real time inside your browser with the Web Audio API. Nothing is recorded, stored or sent anywhere, and the microphone is released when you press Stop.