Live browser microphone meter
Sound Decibel Meter
Estimate sound level in real time, track minimum, average, and peak values, and apply a manual calibration offset.
Meter setup
Your browser will request microphone permission. Audio is analyzed locally and is not uploaded or recorded.
Live sound-level history
Estimated dB over the most recent readings.
Recent sessions
Stored only in this browser tab.
Completed sessions will appear here.
Sound Decibel Meter
Use this sound decibel meter to estimate live noise levels through your device’s microphone. The meter displays the current reading, minimum, average, peak, session duration, relative microphone signal, noise category, and a scrolling level graph.
You can also apply a manual calibration offset and choose a Fast or Slow response. Microphone permission is required, but the plugin processes audio locally and does not record or upload it. Browser microphone access is provided through getUserMedia(), while the Web Audio API supplies waveform samples for analysis.
Important: This is an estimated browser reading, not a certified sound-pressure-level measurement. Device microphones, input gain, automatic processing, and saturation can affect the result.
How to Use the Sound Decibel Meter
- Leave Calibration offset at 0 dB unless you have a trusted reference meter.
- Choose Fast or Slow response.
- Select Start microphone.
- Allow microphone access in your browser.
- Keep the device still while collecting readings.
- Select Stop meter to save the completed session in the current tab.
The large number is the current estimated level. The dashboard also tracks minimum, average, peak, duration, relative signal strength, and a descriptive noise category.
Fast vs Slow Response
| Response | Smoothing time | Best use |
|---|---|---|
| Fast | 125 milliseconds | Following short changes and brief sound events |
| Slow | 1,000 milliseconds | Producing a steadier value for comparison |
The response setting changes how quickly the displayed reading follows the input. It does not improve microphone calibration or convert the result into a professional SPL measurement.
How the Meter Calculates the Estimated dB Level
The plugin uses the following process:
- It requests a mono microphone stream.
- It reads blocks of 2,048 time-domain audio samples.
- It calculates the root-mean-square, or RMS, amplitude.
- It converts RMS amplitude to a logarithmic digital level.
- It adds a fixed mapping offset of 100 dB.
- It adds the manual calibration offset.
- It constrains the displayed result to 0–120 dB.
- It applies Fast or Slow exponential smoothing.
The implemented calculation is:
estimated dB = 20 × log10(RMS) + 100 + calibration offset
RMS represents the effective amplitude of the sampled microphone waveform. Because the decibel calculation is logarithmic, equal numerical changes do not represent equal changes in raw amplitude.
The added 100 dB value maps the microphone’s negative digital amplitude readings into a more familiar positive display range. It is not a device-specific acoustic calibration.
Why the Reading Is an Estimate
A browser receives digital microphone amplitude, not a universally calibrated sound-pressure reference. Two phones or laptops can therefore show different values in the same room.
Possible causes include:
- Different microphone sensitivity
- Hardware or operating-system input gain
- Device-specific frequency response
- Automatic gain control or compression
- Noise suppression
- Microphone saturation during loud sounds
- Microphone placement and orientation
The plugin requests microphone input with automatic gain control, noise suppression, and echo cancellation disabled. Browsers and hardware may not always honor every requested constraint consistently.
Consumer microphone variability and automatic processing are widely recognized limitations of browser sound measurements. Calibrated acoustic monitoring requires known microphone characteristics and a controlled calibration process.
How to Apply the Calibration Offset
The calibration control accepts values from −30 to +30 dB.
A positive offset raises every reading. A negative offset lowers every reading.
For example, when a trusted reference meter shows 64 dB and this tool shows 59 dB under the same steady sound, an offset of +5 dB aligns the displayed estimate at that condition.
For a useful comparison:
- Place both devices close together.
- Use a stable sound rather than speech or intermittent noise.
- Avoid moving either microphone.
- Wait for the readings to settle.
- Enter the difference as the calibration offset.
- Repeat the comparison to check consistency.
At 0 dB, the interface shows Uncalibrated estimate. Any nonzero value shows Offset applied and the selected amount.
A single offset can improve agreement near the reference condition, but it cannot correct microphone frequency response, automatic gain changes, or clipping across every sound level. Some competing meters also offer manual alignment because device readings can be shifted.
How to Read the Results
| Output | Meaning |
|---|---|
| Current | Latest smoothed estimated level |
| Minimum | Lowest retained reading in the session |
| Average | Arithmetic mean of all retained smoothed readings |
| Peak | Highest retained reading in the session |
| Duration | Time since the microphone session started |
| Relative signal | Microphone input strength on the plugin’s internal scale |
| Calibration | Whether a manual offset is active |
The Copy result button copies the current, minimum, average, peak, and calibration values as text.
Relative Signal Is Not a Second dB Reading
Relative signal is calculated from microphone RMS amplitude, scaled against an internal value of 0.25 and capped at 100%.
It is intended to help diagnose the input:
- A very low value can indicate a weak or distant source.
- A higher value indicates a stronger microphone waveform.
- A value near 100% may indicate a strong input, but it does not prove the sound is a specific SPL.
Do not compare the signal percentage directly with the dB result.
Noise Categories
The plugin assigns these descriptive bands:
| Estimated reading | Displayed category |
|---|---|
| Below 30 dB | Very quiet |
| 30–49.9 dB | Quiet |
| 50–69.9 dB | Moderate |
| 70–84.9 dB | Loud |
| 85–99.9 dB | Very loud |
| 100 dB or higher | Extreme |
These are interface labels only. They are not workplace exposure limits, hearing-risk calculations, legal standards, or regulatory classifications.
Live Graph and Session History
The live graph adds a point approximately every 100 milliseconds and displays up to the latest 180 points. Its vertical scale runs from 0 to 120 dB.
Use it to observe changes over time, such as:
- A brief sound peak
- A gradually increasing noise source
- Differences between quiet and active periods
- How Fast and Slow response affect movement
When you stop the meter, the plugin stores the session’s minimum, average, peak, duration, calibration offset, and response mode. It retains up to eight sessions in sessionStorage.
This history exists only in the current browser tab. It is not permanent account-based storage.
Tips for More Consistent Results
Keep the same device, microphone position, orientation, and distance when comparing sessions. Changing any of these can affect the microphone amplitude.
Use Slow response for steadier room-to-room comparisons. Use Fast response when you need to see short changes more clearly.
Avoid covering or touching the microphone. For loud sources, watch for a reading that stops increasing even though the sound becomes louder; that behavior may indicate microphone saturation or automatic compression.
Repeat measurements rather than relying on one moment. The minimum, average, peak, and graph provide more context than the current value alone.
What This Meter Does Not Provide
This online decibel meter does not calculate:
- A-weighted dBA
- C-weighted dBC
- Frequency spectrum
- LUFS loudness
- Equivalent continuous sound level
- Exposure dose
- OSHA or NIOSH compliance
- Legal noise-limit compliance
- Certified acoustic calibration
Some online loudness tools advertise weighting filters, LUFS, or frequency analysis, but those are separate features and are not part of this plugin.
The plugin also does not record, play back, download, or upload microphone audio.
Frequently Asked Questions
How can I measure decibels online?
Select Start microphone, grant permission, and allow the meter to collect live audio samples. It will show an estimated dB reading together with minimum, average, peak, duration, and relative signal strength.
Is this online decibel meter accurate?
It can provide a useful relative estimate, but it is not a certified sound level meter. Accuracy depends on the microphone, device gain, browser processing, calibration, and whether the microphone saturates.
Does the meter display dBA or dBC?
No. The plugin displays an unweighted estimate derived from RMS microphone amplitude. It does not implement A-weighting or C-weighting filters.
What is the difference between current, average, and peak?
Current is the latest smoothed reading, average is the arithmetic mean of retained session readings, and peak is the highest retained reading. Minimum is the lowest value measured during the session.
What do Fast and Slow response mean?
Fast uses a 125 ms smoothing time and follows short changes more closely. Slow uses a 1,000 ms time and produces a steadier display.
How should I calibrate the meter?
Compare it with a trusted sound meter under the same stable sound and enter the difference as the offset. The available calibration range is −30 to +30 dB.
Why do two devices show different dB readings?
Devices use microphones with different sensitivity, gain, processing, and frequency response. Position, microphone orientation, automatic gain control, and saturation can also change the estimate.
What does the relative signal percentage mean?
It shows the strength of the microphone waveform on the plugin’s internal scale. It is useful for identifying weak or strong input, but it is not an SPL measurement or another decibel value.
Does the tool record or upload microphone audio?
No. The plugin analyzes microphone samples locally in the browser and does not use the MediaRecorder API to save audio. Browser recording requires separate recording functionality that this plugin does not create.
Can this replace a professional sound level meter?
No. Use calibrated equipment for workplace compliance, legal evidence, acoustic engineering, or safety-critical measurements. This browser sound meter is intended for reference, comparison, and general noise observation.