Classroom noise meter

Project this on a classroom screen. Students see the noise level in real time and self-correct before the teacher needs to interrupt.

No signup. No downloads. Works on any projector.

What noise levels should I set as thresholds?
Green below 40 dB works for independent reading or silent work. Yellow at 40-65 dB covers group activities and partner work. Red above 65 dB means the class needs to pause. Adjust based on the activity - don't run the meter during intentionally loud periods like presentations.
Does it record what students say?
No. It measures volume only - the amplitude of the audio signal. No speech recognition, no recording, no storage. Audio stays in the browser's local AnalyserNode and is discarded every frame. Nothing leaves the device.
Can students see it from the back of the room?
Yes. The number is rendered at 12-16rem depending on screen size. On a standard projector from 8-10 meters away, it's clearly readable. The color change (green/yellow/red) is visible even if the number isn't.
Does it work on school Chromebooks and projectors?
It works in Chrome, which is what Chromebooks run. Connect to a projector, open the page, click Start. The browser will ask for microphone permission once - after that it remembers. No app installation needed, which avoids school IT restrictions.
Should I leave it on all day?
Most teachers run it during specific work periods where volume tends to creep up - silent reading, independent work, or transitions. Running it during group discussions or presentations doesn't make sense and teaches students to ignore it.