Decibel Meter Online (Sound Level Meter)
Measure ambient sound levels in decibels using your device's microphone. This free decibel meter online works in your browser with no app and displays real-time noise readings, categorizes noise levels, tracks minimum, maximum, and average values, and warns you about potentially harmful noise exposure. Ideal for checking workplace noise, room acoustics, or environmental sound levels.
A decibel meter online is a free browser tool that turns your phone or laptop microphone into a sound level meter. It reads the raw microphone signal with the Web Audio API and shows live, minimum, maximum and average noise levels in decibels, with no app to install and no audio uploaded anywhere.
How Does This Online Decibel Meter Work?
The Sound Level Meter captures audio from your device's microphone using the Web Audio API and analyzes it in real time to determine the ambient noise level. The tool creates an AudioContext with an AnalyserNode that samples the audio waveform at a high rate (typically 44,100 Hz). For each animation frame, the tool reads the time-domain data, computes the Root Mean Square (RMS) amplitude, and converts it to a decibel reading using the formula 20 * Math.log10(rms). This gives a dBFS (decibels relative to full scale) reading that represents the current noise intensity reaching your microphone.
Unlike a professional sound level meter that measures absolute Sound Pressure Level (SPL) in dBA, a browser-based meter measures relative levels based on the microphone's sensitivity and gain settings. The readings are most useful for comparing relative noise levels, identifying noise patterns, and getting a general sense of whether an environment is quiet, moderate, or loud. While the absolute dB values may differ from a calibrated meter, the relative measurements and noise categories provide meaningful guidance for everyday use.
Understanding Decibels and Noise Levels
The decibel (dB) is a logarithmic unit used to measure sound intensity. Because it is logarithmic, every increase of 10 dB represents a tenfold increase in sound energy and roughly a doubling of perceived loudness. Common noise levels include: a quiet library at approximately 30 dB, normal conversation at 60 dB, city traffic at 70 dB, a vacuum cleaner at 75 dB, a rock concert at 110 dB, and a jet engine at 130 dB. Understanding these reference points helps you put your measurements in context.
Noise Exposure Limits and Hearing Safety
Prolonged exposure to loud noise causes permanent hearing damage. The National Institute for Occupational Safety and Health (NIOSH) recommends a maximum exposure of 85 dB for 8 hours, with the permissible duration halving for every 3 dB increase. At 88 dB, safe exposure drops to 4 hours; at 91 dB, just 2 hours; at 94 dB, only 1 hour. The Occupational Safety and Health Administration (OSHA) uses a slightly more lenient 5 dB exchange rate, permitting 90 dB for 8 hours. However, most audiologists recommend following the stricter NIOSH guidelines. Sounds above 120 dB can cause immediate pain and hearing damage even with brief exposure.
Workplace Noise Regulations
Employers are required by law to monitor workplace noise levels and provide hearing protection when levels exceed 85 dBA (NIOSH) or 90 dBA (OSHA). Industries with particularly high noise exposure include construction, manufacturing, music and entertainment, airport ground operations, and mining. If your sound level meter consistently shows readings above 85 dB in your workplace, you should request a professional noise assessment and use appropriate hearing protection such as earplugs or earmuffs rated for your noise environment.
Online Decibel Meter vs a Professional Sound Level Meter
A professional sound level meter is built and calibrated to the IEC 61672-1 standard (Class 1 or Class 2), with a measurement microphone and an acoustic calibrator, so its dBA reading is an absolute sound pressure level you can put in a report. A phone or laptop microphone is designed for speech, and every model has a different sensitivity, so an online decibel meter gives relative readings: excellent for comparing rooms, spotting when noise rises, or checking whether a fix worked, but not a certified measurement.
This meter asks the browser for the raw microphone signal, with echo cancellation, noise suppression and automatic gain control switched off. Those are on by default for calls, and they quietly remove steady background noise and level out loud and quiet rooms — the opposite of what a noise meter needs. For legal, workplace or rental disputes, use a calibrated meter; for everyday checks, the free online decibel meter above is enough.
Tips for Accurate Measurements
For the most accurate readings, place your device on a stable surface away from direct wind or air conditioning vents, which can cause false high readings. Avoid covering the microphone with your hand or case. Keep in mind that built-in laptop and phone microphones have different sensitivities, so readings may vary between devices. For consistent comparisons, always use the same device in similar conditions. The 10-second running average helps smooth out brief spikes and gives a more representative picture of the overall noise environment.
Frequently Asked Questions
How accurate is this online sound level meter compared to a professional one?
This tool provides relative dB measurements using your device microphone, which is useful for comparing noise levels and identifying loud environments. However, it is not calibrated like a professional sound level meter (SLM) and should not be used for regulatory compliance measurements. Professional meters are calibrated to measure absolute Sound Pressure Level in dBA with certified accuracy.
What is the difference between dB and dBA?
dB (decibels) measures raw sound intensity. dBA (A-weighted decibels) applies a frequency weighting that mimics how the human ear perceives loudness — it reduces the contribution of very low and very high frequencies that we are less sensitive to. Professional sound level meters use dBA for noise exposure assessments. This tool measures approximate dB levels from your microphone input.
At what noise level should I be concerned about hearing damage?
Sustained exposure to noise above 85 dB can cause permanent hearing damage over time. At 85 dB, NIOSH recommends a maximum exposure of 8 hours. The safe duration halves with every 3 dB increase: 4 hours at 88 dB, 2 hours at 91 dB, 1 hour at 94 dB. Sounds above 120 dB can cause immediate pain and damage.
Why do the readings vary between my phone and laptop?
Different devices have different microphone sensitivities, positions, and automatic gain control settings. A phone microphone held close to a sound source will register differently than a laptop mic across the room. For consistent comparisons, always use the same device in similar conditions and positions.
Do I need an app to measure decibels on my phone?
No. This decibel meter online runs in Chrome, Safari, Edge or Firefox on Android and iPhone. Tap Start, allow the microphone, and the live dB reading appears. Nothing is installed and the audio is processed on your device, never uploaded.
Can I use this to measure noise levels in my apartment for a noise complaint?
This tool can help you document relative noise levels and patterns, which may support an informal noise complaint. However, for legal proceedings or formal complaints, you typically need measurements from a calibrated, certified sound level meter operated by a qualified professional. The readings from this tool can serve as preliminary evidence but may not be accepted as official measurements.