Free Online Decibel Meter
Measure ambient sound levels in real time using your microphone — with peak tracking, live graph and CSV export.
What is it?
A decibel meter (also called a sound level meter or SPL meter) measures the intensity of sound in decibels (dB), a logarithmic unit that expresses the ratio of sound pressure to a reference level. The standard reference level used in acoustics is 20 micropascals (µPa) — the threshold of human hearing at 1000 Hz. The decibel scale is logarithmic, not linear. This means that a 10 dB increase represents a tenfold increase in sound intensity, and roughly a doubling in perceived loudness. A normal conversation at 60 dB is 100 times more intense than a quiet library at 40 dB, even though it only sounds twice as loud. This tool uses your device's microphone and the Web Audio API's AnalyserNode to continuously measure the frequency content of incoming audio, convert it to an approximate SPL value, and display it on a real-time meter. Readings are logged once per second, displayed on a live sparkline graph and can be exported as a CSV file for further analysis. The tool also shows the peak SPL reached during the session, a running average, and a colour-coded bar meter that progresses from green (quiet) through yellow (moderate) to red (potentially damaging). A dashed red line at 85 dB marks the OSHA Permissible Exposure Limit for occupational noise — the level at which 8 hours of daily exposure begins to risk hearing damage.
How to use it
- Click "Start Measuring" — your browser will request microphone permission.
- Allow microphone access when prompted. The meter will begin displaying readings immediately.
- Watch the dB value, colour-coded bar, peak and average update in real time.
- The sparkline graph shows your sound level history over the last 60 seconds.
- Click "Stop" to pause measurements.
- Click "Export CSV" to download all logged readings (time in seconds, dB value per row).
Why use this tool
Understanding the noise levels in your environment has real health and productivity implications. Prolonged exposure to noise above 85 dB can cause progressive noise-induced hearing loss (NIHL), which is permanent and irreversible. The World Health Organization estimates that 1.1 billion people are at risk of NIHL due to recreational and occupational noise exposure. For office workers and remote workers, sound levels around 50-65 dB are common in open-plan offices and coffee shops — high enough to impair concentration and increase cortisol levels, but low enough that many people do not perceive them as loud. Measuring your actual environment gives you data to act on: move to a quieter space, use noise-cancelling headphones, or advocate for acoustic improvements. The CSV export is useful for anyone who needs to document noise levels over time — for a noise complaint, a workplace safety audit, or a research project. Each row records the elapsed time in seconds and the measured dB value, giving you a timestamped log of the session. All audio data is processed in real time in your browser. Microphone audio is never recorded, stored or transmitted.
Frequently asked questions
How accurate is this decibel meter?
This tool provides a useful approximation of relative sound levels, not a calibrated SPL measurement. Accuracy depends on your device microphone quality, placement and any system-level volume processing. For precision acoustic measurements, use a calibrated hardware SPL meter compliant with IEC 61672.
What is the dangerous noise level?
OSHA (Occupational Safety and Health Administration) sets a permissible exposure limit of 85 dB for 8 hours per day. The WHO recommends keeping recreational noise exposure below 80 dB for 40 hours per week. Above 100 dB, even 15 minutes per day can cause long-term damage.
Does this tool record my audio?
No. The tool only analyses the amplitude of the audio signal in real time using the Web Audio API. No audio is recorded, saved or transmitted anywhere. Microphone access is used only while the meter is running.
What does the CSV export contain?
The CSV contains two columns: "Time (s)" (elapsed seconds since measurement started) and "Decibels (dB)" (the measured value at that second). You can open it in Excel, Google Sheets or any CSV viewer.
Why does the reading fluctuate when it is quiet?
Even in a quiet room, microphones pick up thermal noise (electronic noise from the components themselves) and slight ambient sounds. The meter will never read exactly 0 dB. Background readings of 15-30 dB in a "silent" room are normal.