Sound Level Meter
Press Start and the page shows the estimated sound level from your microphone.
The level is worked out inside this page from the microphone signal. Nothing is recorded, stored or uploaded.
| Level | Typical sound |
|---|---|
| About 30 dB | A whisper or a very quiet room |
| About 50 dB | A quiet office or light rain |
| About 60 dB | Normal conversation |
| About 70-80 dB | Busy traffic, a vacuum cleaner |
| About 85 dB | Heavy traffic. The US NIOSH recommends limiting exposure to 85 dBA for 8 hours. |
| 100 dB and above | Loud music, power tools. Hearing can be damaged in minutes. |
What this tool does
Press Start microphone and allow access, and the meter shows the sound level in estimated decibels, with the lowest, highest and average readings and a chart. Because every microphone is different, set the calibration offset against a reference meter if you need accuracy; otherwise treat the figure as a guide.
Measures the loudness of the microphone signal inside the page.
Converts it to an estimated sound level using a calibration offset you can adjust.
How to use it
- Press Start microphone and allow access.
- Watch the level, minimum, maximum and average.
- To calibrate, play a steady sound beside a reference meter and move the offset until they agree.
- Stop the microphone, and download the readings if you want them.
Why use this tool
Shows the live level from your microphone with the minimum, maximum and energy-average readings and a one-minute chart, and lets you set a calibration offset so it can be matched to a reference meter. People want a rough idea of how loud a room, a machine or a neighbour is. A phone is always to hand, and a clear explanation of what the number does and does not mean is more useful than a precise-looking figure with no basis.
Why we built it
We built the sound level meter to be honest that a phone microphone is uncalibrated, and to let you set the offset against a reference. Check your mic with the microphone test and do the maths with the decibel calculator.
Who this tool is for
- People checking how loud a room is
- Students learning about sound
- Anyone comparing quiet and noisy places
When to use it
- Checking how noisy a room or workplace feels.
- Comparing quiet and loud spots in a house.
- Setting a rough volume level for music or a speaker.
- Teaching about sound and decibels.
How it works
The page reads the microphone signal, works out its root-mean-square amplitude every tenth of a second and expresses it in decibels relative to digital full scale (dBFS). Adding the calibration offset gives an estimated sound level. The average is an energy average: levels are converted to power, averaged and converted back. Noise suppression, echo cancellation and automatic gain are switched off so the signal is as direct as the browser allows.
Example: a steady tone that reads −30 dBFS with an offset of 90 shows 60 dB. If a reference meter says 72 dB for the same sound, raise the offset by 12.
Not a certified instrument. It has no A-weighting, and phone and laptop microphones and automatic processing vary widely. Do not use it to decide on hearing protection or legal noise limits; use a calibrated meter for that.
What you give it, and what you get back
| Item | Details |
|---|---|
| Microphone | Your device's microphone, with your permission. |
| Calibration offset | A number of decibels added to the digital level. |
| Output | The estimated level, minimum, maximum, average, a chart and a CSV of readings. |
Issues you may run into
| What you see | Why it happens | What to do |
|---|---|---|
| The microphone cannot be opened | Permission was denied or another app is using it. | Allow microphone access for this site and close other apps. |
| The reading jumps around | Real sound changes quickly. | Watch the average and chart for the trend. |
| The number does not match a reference meter | Microphones differ. | Adjust the calibration offset. |
Assumptions and limitations
- Estimated, not calibrated.
- No A-weighting or frequency analysis.
Frequently asked questions
How accurate is an online decibel meter?
It is only as accurate as your microphone and your calibration. Use it as a guide, not a measurement for safety or legal purposes.
Is my audio recorded?
No. The level is calculated in the page and the sound is not saved or uploaded.
How do I calibrate it?
Play a steady sound near a reference meter and move the offset until the two readings match.
What decibel level is harmful?
The US NIOSH recommends limiting exposure to 85 dBA over 8 hours, and louder sounds should be shorter. A calibrated meter is needed for a real measurement.
Why does it show a number in a silent room?
Microphones and rooms always have a little background noise.
Is anything sent to a server?
No. Everything runs in your browser and nothing leaves the page.