Classroom noise meter

On this page

• How the noise meter works
• What the colours and numbers mean
• Set it up on a projector or panel
• Calibrate it for your room
• Routines that make it work
• Classroom examples
• When not to use a noise meter
• Accessibility and sensory needs
• Privacy: what happens to the audio
• FAQ
• Related articles
• Sources

How the noise meter works

The noise meter is the Sound widget on the board. It listens through the microphone of the computer that drives your projector or panel, works out how loud the room is about ten times every second, and shows the result as a tall rounded bar that fills from the bottom. Students do not need to understand any numbers. They watch the bar and the face above it.

Setting it up takes four steps:

1. Open the board and add the widget. Go to the free board, open the widget bar at the bottom and choose Sound. A panel titled "Sound Level" appears with an empty bar, a face icon and a round microphone button.
2. Start listening. Click the microphone button. Your browser asks for permission to use the microphone. Choose Allow. The bar starts moving as soon as permission is granted.
3. Place and size it. Drag the widget to where the whole class can see it and pull the corner to make it larger. On a projector, give it a generous share of the screen during group work.
4. Stop when you are done. Click the same button, now showing a stop symbol, to switch the microphone off. Removing the widget from the board also releases the microphone.

If the browser cannot use a microphone, because permission was refused or the computer has none, the widget switches to Manual mode and shows a slider. You can then drag the bar yourself as a visual volume cue, which still works as a "this is the level I want" signal even without live sound.

What the colours and numbers mean

The bar has three zones and a dashed line. The dashed red line sits at 70% of the bar's height and marks the "too loud" point.

A small percentage readout under the bar shows the current level. That number is a relative loudness score from 0 to 100, not a decibel reading. The board takes the microphone signal, splits it into frequency bands using the browser's built-in audio analyser, averages them and scales the result to fit the bar. Two different laptops in the same room can show different percentages for the same noise, because their microphones and input settings differ.

This matters when someone asks whether your room meets a noise guideline. Acoustic standards such as ANSI/ASA S12.60 and the World Health Organization's community noise guidelines describe background noise in decibels measured with calibrated equipment. A classroom display tool cannot tell you that. What it can do well is show students, in real time, whether the room is louder or quieter than the level you set.

Set it up on a projector or panel

A meter that looks fine on a laptop can fail on a wall. Three things decide whether it works in a projected room: where the microphone is, how big the bar appears and what else is making noise.

Microphone position. The computer that drives a projector usually sits at the front, next to you and often under a ceiling fan or projector. Its built-in microphone then hears your voice and the hum around it more than the students at the back. Options, from quickest to most accurate:

• Use the laptop microphone as it is. This is fine in a small room where students sit close to the front.
• Move the laptop to a central table if your cable or wireless display setup allows it.
• Plug in a basic USB microphone on a long cable and put it in the middle of the student tables. This gives the fairest reading of the whole room.
• On an interactive panel running its own browser, check whether the panel has a built-in microphone. If it does, that is the microphone the board will use when the page runs on the panel itself.

When the browser asks for permission, it lets you choose between microphones if more than one is connected. You can also change the choice later in the browser's site settings for myclassscreen.org.

Size for the back row. Before the lesson, stand at the seat furthest from the screen and look at the bar. If you cannot tell amber from green at a glance, make the widget bigger. Press the board's full-screen button so the browser's address bar and tabs disappear, and keep the background plain (the Dots, Grid or Cream backgrounds work well) so the coloured bar stands out. Some projectors wash out green and amber, so check the colours on your actual projector rather than on your laptop screen.

Background noise. Projector fans, heating, air conditioning and hallway traffic all add a steady sound that the meter counts. That is why the bar rarely sits at exactly zero, even in an empty room. Point the microphone away from vents and the projector, and close the door during work where volume matters.

Settings and features

The Sound widget does not have its own sensitivity setting. The threshold line stays at 70%, so you calibrate the meter by changing how much sound reaches it. You have two dials: where the microphone sits and how loud the computer's microphone input is set.

Here is a calibration routine that takes about two minutes with the class present:

1. Name the target. Tell students the volume you want for the next activity, for example "partner voice: only your partner hears you".
2. Let them work. Ask the class to talk at that volume for thirty seconds while the meter runs.
3. Read the bar. At the right volume, the bar should sit in green and only occasionally touch amber.
4. Adjust the input. If the bar jumps into red at a normal partner voice, lower the microphone input level in your computer's sound settings or move the microphone further from the nearest table. If a loud room barely moves the bar, raise the input level or move the microphone closer to the students.
5. Test the top end. Ask one group to get deliberately louder for a few seconds. The bar should climb into amber or red. If it does not, raise the input a little more.

On Windows, the input level is in Settings under System, Sound, then the microphone's properties. On a Mac, it is in System Settings under Sound, Input. On a Chromebook, the input slider is in the quick settings panel under audio settings. Write down the setting that works for each activity type so you can return to it quickly.

Plan to check calibration again when something changes: a different room, the heating switching on, or a move from silent work to group work. Once you know your settings, it takes less than a minute.

Routines that make it work

A noise meter shows what the room sounds like. It works best next to something that shows what the room should sound like. On the board, three widgets do that job well:

• Traffic light. Click it to cycle between green, yellow and red. Agree with the class that green means group talk, yellow means whisper and red means silent work. Students compare the light with the meter at a glance.
• Work Symbols. This widget shows a named mode such as Silence, Whisper, Ask Neighbor or Work Together, which spells out the expectation in words.
• Text. Type one sentence that defines the voice level, such as "Table voice: people at your table hear you, the next table does not."

Introduce the meter as shared information, not as a punishment. In the first week, model each voice level yourself while the class watches the bar, then let students practise. Some classes like a short challenge, such as keeping the bar out of red for the whole of a work block; others respond better to a calm "we are in amber, let's reset" without any game attached.

Keep a short reset routine for when the bar goes red: pause, hands down, count of five in silence, restart at the right level. A visible routine stops the meter turning into a running commentary from you.

You can try all of this before class. Open the board with a noise meter already on it, add a Traffic light next to it and save the layout for tomorrow.

Ways to use it in class

These are examples of how a teacher might set the meter up, not reports from specific classrooms. Every widget mentioned is on the same board, and the classroom widgets hub has a guide for each one. Adjust the timings to your timetable.

• Grade 2 literacy centres, 25 minutes. Meter large in the top right, Traffic light on green, Timer counting down each rotation. When the timer ends, the light goes to red for a silent switch, then back to green.
• Grade 5 science investigation, 40 minutes. Groups talk at table voice while a USB microphone sits on the middle table. A Text widget reads "Table voice". If the bar stays red for more than a few seconds, everyone pauses for the five-count reset.
• Grade 7 independent reading, 20 minutes. Work Symbols set to Silence, the meter small in a corner. Nobody needs to look at it until it moves, which makes it a quiet reminder rather than a centrepiece.
• Indoor break in a shared space. The bar stays visible on the panel and the class tries to keep it out of red until the bell. A librarian or specials teacher can recalibrate in a minute at the start of each session.
• Pack-up time, 3 minutes. A Timer for the clean-up next to the meter gives students two things to beat: the clock and the red line.

When not to use a noise meter

A meter is a tool for one specific problem: volume that creeps up without anyone noticing. It is the wrong tool when:

• Noise is the point of the lesson. Debates, drama, singing, PE and celebrations are meant to be loud. Leaving the meter on sends a mixed message.
• One student is the source. The bar measures the whole room and cannot tell who is talking. Speak to the student privately instead of letting the class blame a table.
• The room is loud for reasons students cannot control. If a heater, a busy corridor or building work keeps the bar in amber, the meter becomes background decoration and students learn to ignore it.
• A student finds it stressful. Some children worry about the bar more than about the task. Make it smaller, move it or turn it off for that lesson.
• You need a formal measurement. Use a calibrated sound level meter, or ask your school's facilities or audiology service, if you need decibel figures.

Accessibility and privacy

The meter never relies on colour alone. Each zone also changes the face icon and the percentage number, and the dashed line marks the limit by position. That helps colour-blind students and students sitting where the projector washes out colour.

The bar moves smoothly and does not flash, and the widget makes no sound of its own, so it will not add noise to a room it is trying to calm. For students with auditory sensitivity, a visual cue can be gentler than a raised voice, but check with the student and with your learning support team before relying on it.

For students with low vision, make the widget large and sit them where they can see it directly. If a student uses a screen reader on their own device, describe the voice level in words as well, using the Text widget or Work Symbols, because the meter itself is visual.

Privacy: what happens to the audio

Families and school leaders often ask whether the meter records students. Here is exactly what the board's code does with the microphone, based on the current source:

• The browser asks for microphone access only when you press the microphone button on the Sound widget.
• The audio stream goes into the browser's built-in Web Audio analyser on your device. The board reads one loudness value from it every tenth of a second and draws the bar.
• The board's code does not record the audio, save it, or send it anywhere. No sound, words or audio files leave the device.
• When you press stop or remove the widget, the board stops the microphone.
• If you save the board, it is stored in your own browser's local storage. The Sound widget saves only its settings and the last level number, never audio.
• Students do not need accounts to see or use the board.

The noise meter reads loudness, not words. For your school's records, point families to the privacy policy, which covers the rest of the site.

If you put the board inside another page with an iframe, the microphone is usually blocked unless that page explicitly allows it. For the noise meter, open the board as a normal link instead of an embed; the embedding guide explains the difference.

Frequently asked questions

Is the classroom noise meter free?

Yes. The noise meter is part of the free board. There is no account, download or payment. It runs in a web browser on the computer connected to your projector or panel.

Does the noise meter record my students?

No. The browser turns the microphone signal into a loudness level on your device, and the board only uses that number to draw the bar. No audio is recorded, stored or uploaded.

Why is the bar always red or never moving?

If it is always red, the microphone input is too high or the microphone is too close to a loud table, so lower the input level or move it. If it never moves, check that the browser has microphone permission and that the right microphone is selected.

Does the percentage show decibels?

No. The percentage is a relative loudness score from 0 to 100 that depends on your microphone and its input level. Use it to compare the room with the level you set, not to measure noise against a standard.

Can I use the noise meter on a Chromebook or smart board?

Yes, if the device has a microphone and the browser is allowed to use it. On managed Chromebooks, your IT team may need to allow microphone access for myclassscreen.org.

Why does the widget say Manual mode?

Manual mode appears when the browser cannot use a microphone, usually because permission was refused. Allow the microphone in the site settings and reload the board, or use the slider to set the bar by hand.

Related articles

• Noise meter strategies that keep working after week one
• Quiet monitor recipes for different activities
• Classroom transitions with visual timers

Sources

1. MDN Web Docs, "MediaDevices: getUserMedia() method": https://developer.mozilla.org/en-US/docs/Web/API/MediaDevices/getUserMedia
2. MDN Web Docs, "AnalyserNode: getByteFrequencyData() method": https://developer.mozilla.org/en-US/docs/Web/API/AnalyserNode/getByteFrequencyData
3. Google Chrome Help, "Use your camera and microphone in Chrome": https://support.google.com/chrome/answer/2693767
4. American Speech-Language-Hearing Association, "Classroom Acoustics": https://www.asha.org/public/hearing/classroom-acoustics/
5. Acoustical Society of America, "Classroom Acoustics" (ANSI/ASA S12.60 resources): https://acousticalsociety.org/classroom-acoustics/
6. World Health Organization, "Guidelines for community noise" (1999): https://www.who.int/publications/i/item/a68672
7. W3C, "Understanding Success Criterion 1.4.1: Use of Color" (WCAG 2.2): https://www.w3.org/WAI/WCAG22/Understanding/use-of-color.html

Try the noise meter now

Open the board, add the Sound widget and press the microphone button. It takes less than a minute, and nothing is installed.

Open the free board