Classroom noise meter traffic light
Put a laptop or tablet by the whiteboard, click “Start traffic light”, go full screen – and the class sees for itself when it gets too loud. You set the thresholds for your room.
How it is calculated
A noise traffic light makes volume visible: instead of saying “shh!” again and again, the light shows the class when it is getting too loud. Here it runs on any laptop, tablet or smartboard with a microphone – nothing to buy.
How it works
- Place the device so the microphone “hears” the room – not right next to noisy equipment.
- Click “Start traffic light” and allow the microphone. “Full screen” fills the projector.
- During normal work, look at the bar and set “Yellow from” and “Red from” just above it.
- Below you see how long the light was green, yellow and red, and how often it switched to red.
How it is calculated
The microphone is opened without automatic gain, the signal is A-weighted according to IEC 61672-1 and smoothed with the calm “Slow” time weighting (1 second). The level from −80 to −10 dBFS is mapped linearly to 0–100. To avoid flicker, each colour stays for at least 2 seconds. While running, the page asks the browser to keep the screen on.
Honest limits
The scale is relative: the same setting means something different on another device or in another room. The light says nothing about whether noise is harmful to health – that takes a calibrated meter. And it does not replace agreements: it works best when the class knows the rules.
Frequently asked questions
How do I set up the noise meter?
Start it during a normal work phase, read the usual value on the bar and set “Yellow from” a little above it and “Red from” higher still.
Does it show decibels?
No. The 0–100 scale is relative because browser microphones are not calibrated. For estimated decibels use the decibel meter tool.
Does it work on a smartboard or projector?
Yes, in any current browser with a microphone. “Full screen” fills the whole display, and “Share” takes your thresholds along as a link.
Is anything recorded in the classroom?
No. The signal is analysed live only; nothing is stored or sent.
Sources and legal basis
- IEC 61672-1:2013 – Electroacoustics – Sound level meters – Part 1: Specifications (A-weighting, time weighting F/S, Leq)
- MDN – MediaDevices.getUserMedia()
- MDN – MediaTrackConstraints.autoGainControl
- MDN – AnalyserNode (Web Audio API)
- MDN – Fullscreen API
- MDN – Screen Wake Lock API
As of:
Related tools
- Online decibel meterMeasure sound level in your browser: level in dBFS, a rough dB(A) estimate, min, max and Leq, plus calibration against a real meter. No app, no recording.
- Online TimerFree online countdown timer: enter any time or tap a 5, 10 or 15 minute preset, get an alarm when time is up, remaining time in the tab. No sign-up.
- Spin the Wheel Online – Free Wheel GeneratorSpin the wheel with your own names, numbers or ideas. Set adjustable odds, remove winners, share by link. Truly random, free, no sign-up.
- Mic test: check your microphoneFree online mic test: live level in dBFS, too quiet or clipping hints and a playback recording. Runs in your browser, nothing is uploaded.
- Altimeter: how high am I?Online altimeter: shows your phone’s GPS altitude with accuracy, average, minimum and maximum, in metres or feet, with a note on ellipsoid vs. sea level.
- Online compass for your phoneFree online compass, no app needed: shows your direction using your phone’s orientation sensor, magnetic or true north with declination. Nothing is sent.