Measure Sound Level
Sound Level Reference
| Level (dB) | Example | Description |
|---|---|---|
| 0-20 | Whisper, rustling leaves | Very quiet |
| 20-40 | Quiet room, library | Quiet |
| 40-60 | Normal conversation | Moderate |
| 60-80 | Busy traffic, vacuum cleaner | Loud |
| 80-100 | Lawn mower, motorcycle | Very loud |
| 100+ | Rock concert, chainsaw | Potentially harmful |
About This Sound Level Meter
This sound level meter is a browser-based tool that measures the relative loudness of sound captured by your microphone in decibels (dB). It uses the Web Audio API to analyze your microphone's audio signal in real-time and display a dB reading with peak hold and running statistics.
How It Works
- Microphone capture: When you click "Start Measuring," the browser requests access to your microphone via the MediaDevices API.
- Signal analysis: The audio stream is fed into a Web Audio API analyser node. The meter reads time-domain samples at approximately 60 frames per second.
- RMS calculation: Each frame, the tool computes the Root Mean Square (RMS) of the audio samples — a standard measure of the average energy in the signal.
- dB conversion: The RMS value is converted to a decibel scale using the formula
dB = 20 × log₁₀(RMS), referenced to the maximum digital signal level (dBFS — decibels relative to full scale). The result is normalized to a 0–100 display range.
Limitations
- Relative, not absolute: This is not a calibrated Sound Pressure Level (SPL) meter. Readings are relative to your microphone's sensitivity and gain settings. For accurate SPL measurements, use a calibrated Class 1 or Class 2 sound level meter.
- No frequency weighting: Professional meters apply A-weighting (dBA) to match human hearing sensitivity. This tool uses unweighted (linear) measurement, which may over-represent low-frequency content.
- Microphone variation: Results depend heavily on your device's microphone quality, frequency response, and any automatic gain control applied by the browser or operating system.
Privacy
All audio processing happens entirely in your browser. No audio data is recorded, stored, or sent to any server. The microphone stream is stopped immediately when you click "Stop" or leave the page.
Learn More
For a detailed explanation of how the decibel scale works, safe noise exposure limits, and what common dB levels mean, read our guide: How Decibels Work: Understanding Sound Levels and the dB Scale.
Related Tools
- FFT Spectrum Viewer -- Real-time frequency spectrum analyzer with bar graph display
- Music Visualizer -- Turn music into animated geometric shapes, circular waveforms, and radial
- Metronome -- Simple metronome with adjustable BPM and time signatures
- White Noise Generator -- Generate white, pink, and brown noise for focus or relaxation
Related Tools
View all toolsOpus Metadata Viewer
Drag and drop an .opus file to view its embedded metadata and transcription
Tone Generator
Generate pure sine, square, and sawtooth tones at any frequency
Metronome
Simple metronome with adjustable BPM and time signatures
Frequency to Note Converter
Convert frequency (Hz) to musical note name and cents offset
Audio Timer
Timer with customizable audio alerts and chimes
White Noise Generator
Generate white, pink, and brown noise for focus or relaxation
Sound Level Meter FAQ
What does this sound level meter measure?
It measures the relative loudness of sound captured by your microphone in decibels (dB). It calculates the RMS (root mean square) of the audio signal and converts it to a decibel scale relative to the maximum digital signal level (dBFS). The reading is relative to your microphone's sensitivity, not an absolute SPL value.
Is this a calibrated sound pressure level (SPL) meter?
No. This is an uncalibrated browser-based meter. It uses your device's microphone, which is not calibrated against a known reference. Readings are useful for comparing relative loudness between environments, but should not be used for workplace safety compliance or regulatory measurements. Professional SPL meters (Class 1 or Class 2) are needed for accurate absolute readings.
Why do the dB values look different from a professional meter?
Several factors cause differences: your microphone's sensitivity and frequency response, browser-level automatic gain control, ambient electrical noise, and the lack of A-weighting. Professional meters apply standardized frequency weighting (typically dBA) and are calibrated against reference sound sources.
What do the Peak, Average, and Min values mean?
Peak is the highest dB reading recorded since you started measuring (or last reset). Average is the running mean of all readings. Min is the lowest non-zero reading. Together, they help you understand the dynamic range of your sound environment.
Does this tool record or store my audio?
No. All audio processing happens locally in your browser using the Web Audio API. No audio data is sent to any server. When you stop the meter or close the page, the audio stream is terminated.
What is a safe noise level?
Prolonged exposure to sound above 85 dB SPL can cause gradual hearing damage. The higher the level, the less time is safe — 85 dB for 8 hours, 100 dB for 15 minutes. However, since this tool provides relative (not calibrated) readings, use a professional meter for safety assessments.
Can I use this on my phone?
Yes, this tool works on most modern mobile browsers that support the Web Audio API and microphone access (Chrome, Safari, Firefox). You'll need to grant microphone permission when prompted. Note that phone microphones vary significantly in sensitivity and frequency response.
What is dBFS vs dB SPL?
dBFS (decibels relative to full scale) measures audio levels in digital systems where 0 dBFS is the maximum possible signal. dB SPL (sound pressure level) measures physical sound pressure in air relative to 20 micropascals. This tool shows dBFS-derived values from your microphone's digital output, which is why readings differ from a calibrated SPL meter.