Decibel Meter
Measure ambient sound level in dB with a free online decibel meter.
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What is Decibel Meter?
A decibel meter is a browser-based sound level meter that measures ambient noise through your microphone using the Web Audio API. It computes the RMS level of each audio frame, displays it in dBFS on a live color-coded meter, tracks peak, average, and minimum values, and estimates absolute dB SPL with an adjustable calibration offset - no app installation, recording, or uploads required.
Key Benefits
- Instant ambient noise checks without installing a mobile app
- Live peak tracking helps avoid clipping when setting recording gain
- Calibration offset turns relative dBFS into a usable dB SPL estimate
- Runs 100% locally - audio never leaves your device
Common Use Cases
- •Checking how loud an office, room, or workspace is before recording
- •Verifying microphone input levels before streaming or a video call
- •Comparing ambient noise against common reference levels like conversation or traffic
- •Monitoring noise levels during events, rehearsals, or equipment tests
How to Use the Decibel Meter
- Start measuring: Click Start Measuring and allow microphone access when your browser asks. The meter begins reading your microphone signal immediately.
- Read the meter: Watch the big dBFS readout and the color-coded level bar. Peak, average, and minimum values update live below the meter.
- Calibrate for SPL: Browsers report relative levels, so adjust the calibration offset slider until the estimated dB SPL matches a reference meter. 94 dB SPL at 0 dBFS is a common starting point.
- Compare and export: Check the reference table to see how your reading compares to common sounds, then click Copy Report to export all measurements as text.
Key Features
- Live dBFS meter with a color-coded level bar and peak marker updated every frame
- Peak, average, and minimum level statistics with one-click reset
- Adjustable calibration offset to estimate absolute dB SPL from relative dBFS
- Reference table of common sound levels from whisper to rock concert with live highlighting
- Copy a text report of all measurements, microphone, and sample rate - fully offline and private
Frequently Asked Questions
How accurate is this decibel meter?
It measures relative levels (dBFS) accurately from your microphone signal, but absolute dB SPL depends on your microphone hardware and browser processing. Use the calibration offset to match a reference meter - treat readings as estimates, not certified measurements.
Why does the meter show dBFS instead of dB SPL?
Browsers expose the raw digital audio signal, where 0 dBFS is the maximum level before clipping. Converting to absolute sound pressure (dB SPL) requires knowing the microphone sensitivity, which varies per device. The calibration offset slider bridges that gap.
Is my audio recorded or uploaded anywhere?
No. The microphone signal is analyzed in real time inside your browser using the Web Audio API and discarded immediately. Nothing is recorded, stored, or sent over the network.
Why do the readings seem lower than a phone SPL app?
Phone apps often apply their own calibration and weighting curves, and laptop microphones usually have automatic gain limits. Raise the calibration offset until the estimate matches your reference, and disable any OS-level noise suppression if possible.