How to use the decibel meter
- Press Start measuring and allow the microphone. The page switches off the browser's echo cancellation, noise suppression and automatic gain, which change the level, and tells you if it can't.
- The big number is the level now (A-weighted, Fast). Give it 10 seconds before trusting the average, L10 and L90.
- To trust the numbers, calibrate once per microphone. For a complaint, start a noise log; for a class, open the classroom light.
How accurate is a phone or laptop sound meter?
A browser only gives the page digital samples, so the meter measures dBFS (decibels below the loudest digital value) and adds an offset to estimate dB SPL. The offset depends on the microphone and input volume, and browsers don't report it. Until you calibrate, the page uses 100 dB on computers and 112 dB on phones and tablets, from the sensitivity Android's compatibility rules recommend for voice recognition. Chrome records through another input that can keep automatic gain on, and Apple publishes no figure, so it is only a starting point. Readings can be 10 dB or more off: in NIOSH's 2014 tests, the least accurate meter apps on iPhones and iPads averaged about 13 dB(A) too low, and a 2016 follow-up found calibrated external microphones far more reliable than built-in ones (Kardous and Shaw, J Acoust Soc Am).
To calibrate, follow the Calibrate tab with a reference meter and a steady sound, such as pink noise from the speaker test on another device. Afterwards, expect a few dB of error; built-in microphones still miss deep bass and clip at very high levels. This is an estimate, not a certified IEC 61672 meter.
How to read the numbers
| Reading | What it means |
|---|---|
| dB(A), dB(C), dB(Z) | Frequency weighting. A follows how loud sounds seem to people and is used for most limits. C keeps the bass (music, engines, peaks). Z is flat. |
| Fast, Slow | How quickly the level follows the sound: Fast averages over 125 ms, Slow over 1 s and is steadier to read. |
| Leq (average) | The energy average: a loud minute raises it far more than a quiet one lowers it. |
| Max, Min | The highest and lowest Fast or Slow level. |
| L10, L90 | The level exceeded 10% of the time (loud moments) and 90% (the background). |
| Peak | The highest instantaneous C-weighted value (LCpeak), whatever weighting is selected. |
The A, C and Z filters follow IEC 61672-1:2013 and run on every sample; they match the standard's table within 0.15 dB up to 10 kHz.
Decibel chart of common sounds
| Sound | Typical level |
|---|---|
| Whispering | 30 dB |
| Refrigerator | 40 dB |
| Dishwasher | 45–65 dB |
| Normal conversation | 60–70 dB |
| Washing machine | 70 dB |
| Traffic noise inside a car | 80 dB |
| Lawnmower | 80–100 dB |
| Leaf blower | 90 dB |
| Movie theater | 74–104 dB |
| Motorcycles and dirt bikes | 80–110 dB |
| Headphones at maximum volume, sporting events and concerts | 94–110 dB |
| Rock concerts, parties and nightclubs | 95–115 dB |
| Sirens | 110–129 dB |
| Fireworks | 140–160 dB |
Sources: NIDCD, Noise-Induced Hearing Loss (updated April 2025); CDC, Listen Up! Protect Your Hearing; CDC Vital Signs, Too Loud! For Too Long! (2017). Outdoors, a small source's level drops about 6 dB each time you double your distance.
How loud is too loud?
- At work: NIOSH recommends at most 85 dB(A) averaged over 8 hours, halving the time for every 3 dB more: 4 hours at 88, 1 hour at 94 and 15 minutes at 100 dB(A) (Criteria for a Recommended Standard: Occupational Noise Exposure, 1998). OSHA's legal limit is 90 dB(A) for 8 hours with a 5 dB exchange rate, and a hearing conservation program is required from 85 dB(A) (29 CFR 1910.95). For bangs, NIOSH's ceiling is 140 dBA for any noise, OSHA advises impulse noise should not exceed 140 dB peak, and the EU's limit is 140 dB(C) peak (Directive 2003/10/EC), the LCpeak shown above.
- Listening: the WHO-ITU safe listening standard (ITU-T H.870, 2018) allows adults a weekly dose equal to 80 dB(A) for 40 hours (75 dB(A) for children), and WHO's 2022 standard for venues keeps audiences below 100 dB LAeq over any 15 minutes.
- At home and school: WHO's Guidelines for Community Noise (1999) suggest 30 dB LAeq in bedrooms at night (single noises below 45 dB LAmax) and 35 dB LAeq in classrooms during lessons; WHO Europe (2018) recommends road traffic below 53 dB Lden and 45 dB at night.
The exposure line under the readings applies the NIOSH and OSHA formulas to your measured average: a guide, not a diagnosis. If your ears ring or sound muffled after noise, or your hearing changes, see a doctor or audiologist; sudden hearing loss needs care the same day.
Noise logs and the classroom light
The noise log writes a row per 1, 5 or 15 minutes with Leq, the maximum and its time, L10, L90 and the seconds really measured, and exports CSV or a PDF report. Officials usually measure with certified meters, but a timestamped log shows when the noise happens.
The classroom light fills the screen with a traffic light that follows the Slow level. Set amber and red a little above the level of quiet work; the optional alarm sounds after 2 seconds of red, at most every 10 seconds.
After 10 seconds of measuring, Share result makes a link with the readings on screen: the average, maximum and minimum in the weighting you chose, how long you measured, and whether your microphone was calibrated. Never the sound, your microphone's name or its calibration offset. Whoever opens it sees those readings with the same caveat: an estimate from a phone or laptop microphone, not a certified meter.
Nothing is recorded or uploaded. To check the microphone, use the microphone test, and for your ears, the online hearing test.