Classroom Noise Meter

A traffic light noise meter for the classroom, with an adjustable limit and a fullscreen display for the projector. Runs in your browser, nothing is recorded.


55 / 100
100%
Press Start listening and allow the microphone when your browser asks. Set the limit where the room should stay below, and seconds over the limit so one cough does not trip the alert. Adjust sensitivity until a normal working buzz sits comfortably in the green.
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Not listening
Now
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Average
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Peak
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Times over
0

The microphone is read in your browser and nothing is uploaded or recorded. Only a loudness number is taken from the audio, and it is gone the moment the next reading replaces it.

How the meter works

The page opens your microphone, measures how much the waveform is moving many times a second, and turns that into a single loudness number. Quiet classroom chatter sits low, a shout spikes it. The reading is smoothed over a short window so a chair scraping does not swing the display, while a room that is genuinely getting louder shows up within a second or two. When the level stays above your limit for longer than the delay you set, the display turns red and the counter goes up. Every browser noise process is switched off when the microphone is opened, in particular automatic gain control, which would otherwise quietly turn the volume back down and make the whole meter useless.

Why the scale is 0 to 100 and not decibels

Because a browser cannot know how sensitive your microphone is. A real sound level meter is calibrated against a known reference; a laptop microphone is not, and the same room will read differently on a Chromebook, an iPad and an external USB microphone. Any tool that shows you a confident dB figure from a plain web page is inventing the calibration. So this one gives you a relative 0 to 100 scale instead, and a sensitivity control to set it against your own room. That is honest about what the measurement is, and for classroom use it is also the more useful number: what matters is louder or quieter than the level you agreed on, not an absolute physical figure.

Setting it up for a class

Start with the class working at the level you want, then turn sensitivity up or down until the reading sits in the middle of the green. Set the limit a little above that, so ordinary work does not trip it. Set seconds over the limit to two or three; at zero the display flickers red on every dropped book, which children quickly learn to ignore. Then press Fullscreen and put it on the projector or the interactive whiteboard. Keep the device somewhere central rather than on your own desk, since a microphone a metre from one talkative table will read that table rather than the room.

What happens to the audio

Nothing leaves the device. The audio goes from the microphone into an analyser inside your browser, a loudness figure is read out of it frame by frame, and the audio itself is discarded immediately. It is never written to disk, never sent to our server and never recorded. Nothing is connected to the speakers either, so there is no risk of feedback howl. Pressing Stop or closing the tab releases the microphone straight away, and your browser turns off its recording indicator.

Worth knowing

  • Fullscreen on a projector is what makes this work: children respond to a display they can all see.
  • Set the delay to two or three seconds, or the display flashes red at every dropped pencil.
  • Recalibrate sensitivity if you move rooms or change device; microphones vary enormously.
  • The peak and average reset with the counters, which is useful between lessons.
  • Nothing is uploaded or recorded. The audio never leaves your browser.

Frequently asked questions

No. The audio goes into an analyser in your browser, a single loudness number is read from it, and the audio is thrown away immediately. Nothing is written to disk, nothing is sent to our server, and there is no recording to retrieve afterwards. Pressing Stop releases the microphone at once.

Because it cannot know one. Decibels of sound pressure need a calibrated microphone, and a browser has no way to find out how sensitive yours is. The same room would read differently on every device. A 0 to 100 scale with a sensitivity control is honest about that, and for classroom management the comparison against your own limit is the number that matters anyway.

Reading a microphone always needs your consent, which is exactly as it should be. Allow it for this site and the meter starts. If you refused by accident, open the site settings in your browser, clear the microphone permission and press Start listening again.

There is no universal number, because the scale is relative to your microphone. Have the class work at the level you actually want, adjust sensitivity until that sits in the middle of the green, then put the limit a little above it. Quiet reading, paired work and group work all deserve different settings.

Yes, that is what the fullscreen button is for. The traffic lights and the number scale up to fill the screen, so they read from the back of the room. Press Escape or the exit button to come back.

Usually sensitivity is set too low for that microphone, so try raising it. If the number barely moves at all, another program may have the microphone, or the browser may be listening to the wrong input device: check which microphone is selected in your system sound settings.

Yes, on any recent browser that can open a microphone. On a shared class tablet remember that the microphone stays open until you press Stop or close the tab, so the recording indicator will stay lit while the meter is running.

Because a live microphone can only be read in the browser; there is no way to do it on a server. The meter is the only part that needs it. The settings, the explanations and these answers are all delivered as ordinary pages and work whether scripting is on or off.

How does a classroom noise meter work?

It opens the microphone in your browser and turns the sound into a relative 0 to 100 loudness reading with a traffic light display. Set a limit and a delay, press fullscreen for the projector, and the display turns red when the class stays over the line. Nothing is uploaded or recorded, and the audio never leaves the device.