Decibel Meter: Free Online dB Meter for Noise Levels
Overview
Decibel Meter. Click Enable Microphone and the Decibel Meter turns your microphone into a sound level meter, reading Live, 5s Average, and Peak dB levels with a choice of A, C, or Z frequency weighting. Run the built-in hand-rub calibration first, since your device's microphone isn't calibrated for absolute SPL out of the box. Run the vocal range test to see exactly what's working and what isn't.
Curious how loud your street, office or workshop really gets? This free online decibel meter turns the microphone on your smartphone, laptop or tablet into a live gauge of ambient sound, with no app, no download and no sign-up. You get real decibel levels in seconds, so you can tell whether the volume around you is fine for sleep, work or your ears.
How to Use This Browser Decibel Meter
Everything runs inside your browser through the Web Audio API, which reads the signal from your built-in microphone or a plugged-in one and converts it into a reading many times per second.
Allow Microphone Access
Press Start and accept the browser prompt. Without microphone access the page has no signal to analyse, so nothing appears. You can revoke permission at any time in your browser settings.
Watch the Live Sound Levels
The big number shows sound levels as they change. A fast update rate catches short bursts, a slow one gives a steadier figure, and the display scale switches between an everyday 0-130 range and raw full-scale values.
Your Privacy While You Measure
Your audio is processed locally and never recorded. No sound leaves your device, nothing is stored on a server, and closing the tab ends the session.
What a Sound Level Meter Actually Measures
The meter reports sound pressure in decibels, the unit acoustics uses because human ears handle an enormous range of sound intensity. The level compares a measured intensity with a reference:
$$L = 10 \log_{10}\left(\frac{I}{I_0}\right)$$
Decibels on a Logarithmic Scale
Because the logarithmic scale compresses that range, every 10 dB step means a tenfold change in intensity. A reading of 89 dB carries ten times the energy of 79 dB, even though the numbers look close. Inside the browser the raw signal starts as dBFS (decibels relative to full scale), which the page offsets into familiar values.
Frequency Weighting: dBA, dBC and dBZ
dBA trims bass and extreme treble to match human hearing, so it is the default for noise checks. dBC keeps more low-frequency energy for engines and subwoofers, and dBZ applies no frequency weighting at all. Unlike tools that report LUFS, RMS and true peak for a recorded file, this meter weighs the live loudness of the room around you.
Reading Your dB Meter: Peak, Minimum and Maximum
A single number can mislead, so a good db meter online keeps running statistics for the whole session:
- Min/max/average: the quietest moment, the loudest sustained level and the overall mean of the session.
- Spikes: the highest instant, such as a dropped tool or a slammed door.
- Minimum readings show the floor of a space; maximum readings show its worst moments.
Peak Hold and the History Graph
Peak hold freezes the top value for a few seconds so you can read it. The history graph plots the level over time, and a spectrum analyzer view uses an FFT to split the sound into bands, showing whether the energy is a low hum or a high whine.
Color-Coded Noise Tiers
The color-coded display gives each reading a noise tier: green for quiet, yellow for moderate and red for levels where long exposure becomes risky.
Common Sound Levels: A Sound Meter Decibel Chart
Compare your reading with this decibel chart of typical sources. The WHO suggests keeping night-time noise in bedrooms near 30 dB for restful sleep.
| Level | Typical source | What it means |
|---|---|---|
| 0 dB | Threshold of hearing | Faintest sound a healthy ear detects |
| 30 dB | Whisper, quiet room | Ideal for sleep |
| 40 dB | Library, refrigerator | Calm background |
| 60 dB | Normal conversation | Comfortable everyday noise |
| 80 dB | Busy traffic, vacuum cleaner | Tiring over long periods |
| 90 dB | Lawnmower | Risky after a few hours |
| 110 dB | Rock concert | Damage within minutes |
| 130 dB | Jackhammer at close range | Painful |
| 140 dB | Fireworks | Immediate harm possible |
A decibel sound meter reading between 30 and 85 dB covers almost everything you meet indoors.
Choosing a Quieter Bedroom with a Free Decibel Meter
I'm deciding whether to move my bed from the street-facing room to the back of the flat, or to pay for secondary glazing instead. The answer comes back clearly: the front room averages 38.6 dB at night, the back room 31.2 dB, so moving the bed gets me most of the way to the WHO night target of about 30 dB for free.
The method matters more than the tool. At 1:15 a.m. I set the meter to dBA, put the phone face up on the pillow, switch off the ceiling fan and close the window. I run a 60-second session in each room and write down the session average, not the live number, because a single passing car pushes the front room to a 51.3 dB peak.
Before trusting either figure, I measure inside a closed wardrobe stuffed with coats. It still reads 29.4 dB. That is roughly the phone microphone's own noise floor, not real sound, so I subtract it on an energy basis:
$$L_{ ext{room}} = 10 \log_{10}\left(10^{38.6/10} - 10^{29.4/10} ight) = 38.0\ ext{dB}$$
The front room barely changes (38.0 dB). The back room drops from 31.2 to 26.5 dB, which shows its reading is mostly the microphone hearing itself.
| Session | Meter average | After removing the 29.4 dB floor |
|---|---|---|
| Front room, window shut | 38.6 dB | 38.0 dB |
| Front room, window open | 45.8 dB | 45.7 dB |
| Back room, window shut | 31.2 dB | 26.5 dB |
The 7.4 dB gap between the rooms means about 5.5 times less sound energy reaching the back pillow. To bring the front room down to 30 dB, glazing would need to cut 8.6 dB, which is a demanding specification for a retrofit.
The edge case worth knowing: once a reading sits within about 3 dB of the floor test, your meter can no longer tell you how quiet the room really is, only that it is quieter than the phone can measure. I wouldn't compare two quiet rooms without running that wardrobe check first. My next step is to repeat the back-room session at 5:30 a.m., when the delivery lorries start, before I move any furniture.
Safe Exposure Time from a Noise Meter Reading
A noise meter reading becomes useful for occupational health once you turn it into time. NIOSH allows 85 dB for 8 hours and halves the time for every 3 dB above that (OSHA uses a looser 90 dB and 5 dB rule):
$$T = \frac{8}{2^{(L-85)/3}}\ \text{hours}$$
Worked Example: An 89 dB Garage Workshop
Say you run a circular saw and sander in your garage and log one session:
- Quietest 71.4 dB between cuts, average 89.0 dB, loudest instant 103.2 dB.
- \(T = 8 \div 2^{(89-85)/3} = 8 \div 2.52 = 3.17\) hours, about 3 hours 10 minutes.
- Cut the noise level to 86 dB with a quieter blade and the limit rises to 6.35 hours.
Hearing Damage and When to Wear Protection
If your session average stays above 85 dB or the red tier keeps lighting up, damage to your ears builds slowly and without pain. Ringing ears afterwards are an early warning, so wear hearing protection whenever the meter shows that, and check headphones by holding an earcup to the mic at your usual volume.
How Accurate Is an Online SPL Meter?
An online SPL meter relies on consumer microphones, which are not calibrated and often apply automatic gain to the audio signal. Expect accuracy within a few dB in the middle of the range and wider gaps near the quiet and loud extremes, so treat each figure as a reference estimate of relative loudness. A certified Class 2 professional meter is still needed for legal or workplace compliance.
Calibration Offset with a 1kHz Tone
Play a steady 1kHz tone, hold a reference meter beside your device and adjust the calibration offset until both match. The correction is most reliable for sounds close to that test tone.
Tips for Better Loudness Meter Readings
Hold the device about 1 meter from the source, keep the mic uncovered and use an external mic if you have one. Readings reflect perceived loudness only as well as the mic hears it.
Background Noise and Reflective Surfaces
Measure the background noise first: if your target is not clearly louder, ambient noise dominates the result. Wind across the mic inflates readings, and walls or hard floors add sound reflections, so keep away from reflective surfaces.
Where to Measure Noise with a Noise Level Meter
An online sound level meter is handy anywhere environmental noise affects your day.
Room Noise for Sleep and Focus
Check bedroom levels at night before and after soundproofing, and test a workspace before deciding it suits deep focus.
Home Office, Classroom and Recording
Teachers run a session during group work to see when the classroom gets loud, and creators take a 60-second reading in a home office before recording podcasts or tuning speakers: a background under about 35 dB keeps clean audio easy.
Apartment Hunting with a Decibel Meter Online
Visit a flat at rush hour, or log repeated readings and audio notes before raising noise complaints. For this, the best decibel meter is the one you open in seconds, and a sound decibel meter in your browser is exactly that.
Frequently Asked Questions
- Is this decibel meter free to use?
- Yes. It runs in your browser with no download, account or usage limit. Allow microphone access and the reading starts straight away.
- Do I need a special microphone?
- No. The built-in microphone on a phone, laptop or tablet works. An external USB mic usually gives steadier readings, and the calibration offset lets you line any mic up with a reference meter.
- Is my audio recorded or uploaded?
- No. Sound is processed locally in your browser to calculate the level and is discarded immediately. Nothing is stored or sent to a server.
- How accurate is a phone or browser decibel meter?
- Consumer microphones are not calibrated, so readings can differ by several dB between devices and are least reliable in very quiet rooms and at very loud levels. Use it to compare rooms and spot problems, and use a certified meter for legal or workplace compliance.
- Why does my reading differ from a phone app?
- Each device has a different microphone and each app uses its own processing and weighting, so gaps of 5-10 dB between devices are normal. Calibrating against a reference meter with a 1kHz tone narrows the gap.
- What is a safe noise level?
- Around 30 dB is ideal for sleep, and daily exposure should stay under 85 dB averaged over 8 hours. Under the NIOSH rule, each 3 dB above 85 halves the safe time.
- What is the difference between dBA, dBC and dBZ?
- dBA weights the reading the way human hearing responds and is the usual choice for noise checks. dBC keeps more low-frequency energy, which suits engines and subwoofers, and dBZ applies no weighting at all.