Decibel Shield
Online Decibel Meter
Press Start and this page measures the sound level around you, in decibels, using your device microphone. It runs entirely in your browser — no app to download, no sign-up, and no audio is ever recorded or uploaded. Readings are uncalibrated estimates (about ±10 dB); for calibrated accuracy you need a dedicated meter or a calibrated app.
Your browser will ask for microphone access. Nothing is recorded or uploaded — the analysis runs entirely on your device.
Defaults are tuned per device; nudge until it matches a reference meter you trust. Saved on this device.
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What this tool does
Whether you call it a sound level meter, an SPL meter, a dB meter, a noise meter, a loudness meter, or a decibel reader, this tool does the same job: it shows the sound pressure level around you in decibels. The meter reads your microphone with the Web Audio API about ten times a second, converts the signal energy to decibels, and applies a fixed offset to approximate sound pressure level (dB SPL). You get a live readout, the session minimum, average, and maximum, an optional live frequency spectrum showing which pitches the sound is made of, and an optional A-weighting filter that approximates how human hearing emphasises mid-range frequencies — the same weighting, written dB(A), that noise regulations use.
How to measure decibels right now (3 steps)
- Press Start and allow the microphone. The meter runs in your browser on a phone or laptop — no app to download, no email or sign-up, and nothing is recorded.
- Hold the device toward the sound for about 30 seconds. The readout shows the live level plus your session minimum, average and maximum in decibels.
- Read the number against the scale. Normal conversation sits near 60 dB and sustained exposure above the 85 dB line risks hearing damage (NIOSH) — the decibel chart places 40+ everyday sounds on that scale. Remember the reading is a ±10 dB estimate.
Sound level guide: what your reading means
The meter's readout shifts colour at 70, 85 and 100 dB, the same lines this table uses. Every example is a published CDC, NIOSH, NIDCD or ASHA figure from the decibel levels chart.
| Reading | Sounds like | What it means |
|---|---|---|
| Under 30 dB | Ticking watch (20 dB), soft whisper (30 dB) | Near silence. Safe at any duration. |
| 30 to 50 dB | Refrigerator hum (40 to 45 dB), moderate rainfall (50 dB) | Quiet room. The WHO night-time target for sleep is 45 dB outdoors. |
| 50 to 70 dB | Normal conversation (60 to 70 dB), window air conditioner (60 dB) | Everyday levels. The EPA treats 70 dB or lower as safe at any duration. |
| 70 to 85 dB | Vacuum cleaner (70 to 75 dB), alarm clock (80 dB), city traffic heard from a car (80 to 85 dB) | Loud but under the NIOSH limit. Tiring over a workday, and the readout changes colour here. |
| 85 to 100 dB | Shouted conversation (90 dB), riding a subway (90 to 95 dB), motorcycle (95 dB) | Hearing risk with time. NIOSH allows 8 hours at 85 dB and about 15 minutes at 100 dB. |
| 100 to 120 dB | Car horn at 5 m (100 dB), rock concert (105 to 110 dB), chainsaw (110 dB) | Minutes or less. Under 2 minutes a day at 110 dB. |
| 120 dB and up | Thunderclap nearby (120 dB), firecrackers (140 to 150 dB), gunshot at the ear (140 to 165 dB) | Immediate injury is possible. No safe duration. |
For any single number, the how loud is 60 decibels series covers 62 levels from 10 to 150 dB, and the how loud is a chainsaw series covers the sounds themselves.
Safe exposure time by decibel level (NIOSH and OSHA)
Once your average reading passes 85 dB, safety becomes a budget of time. NIOSH recommends no more than 8 hours a day at 85 dB(A) and halves that with every 3 dB. The OSHA legal limit for US workplaces is looser: 8 hours at 90 dB(A), halving every 5 dB, with 85 dB as the action level that triggers a hearing conservation programme. Read your session average against this table, not the peak.
| Average level | NIOSH (85 dB, 3 dB exchange) | OSHA (90 dB, 5 dB exchange) |
|---|---|---|
| 85 dB(A) | 8 hours a day | No limit (85 dB action level) |
| 88 dB(A) | 4 hours a day | No limit (85 dB action level) |
| 91 dB(A) | 2 hours a day | 6 to 8 hours |
| 94 dB(A) | 1 hour a day | 4 to 6 hours |
| 97 dB(A) | 30 minutes a day | 3 hours |
| 100 dB(A) | 15 minutes a day | 2 hours |
| 103 dB(A) | 8 minutes a day | 1 to 1.5 hours |
| 106 dB(A) | 4 minutes a day | 30 min to 1 hour |
| 109 dB(A) | 2 minutes a day | 30 min to 1 hour |
| 112 dB(A) | 56 seconds a day | 15 to 30 min |
| 115 dB(A) | 28 seconds a day | 15 min |
The full tables, with the reasoning behind the two exchange rates, are on safe decibel levels and OSHA noise exposure limits.
How accurate is it?
Honest answer: it is an estimate, not a measurement instrument. Phone and laptop microphones are built for voice, not metrology, and none of them are calibrated. Expect readings within roughly ±10 dB of a true SPL meter, with the largest errors at very quiet and very loud extremes. That is plenty to answer “is this room around 60 dB or 90 dB?” — it is not evidence for a noise complaint or an OSHA/NIOSH compliance check. The default offset is tuned per device class — iPhone microphones report quieter signals than laptop microphones for the same sound — and the calibration control under the meter lets you nudge readings to match a reference meter you trust. Our accuracy & calibration page covers the error envelope and the offsets in full, and the FAQ explains how phone meters compare to dedicated SPL meters.
A measurement routine that holds up
- Clear the microphone. Take the phone out of a thick case, keep fingers off the mic, and hold the device at arm's length pointed at the source. Handling noise and wind read as tens of decibels of nothing.
- Calibrate if you can. If you have access to any reference meter, play a steady sound such as a fan and adjust the calibration control until the two agree. That setting is saved for next time.
- Measure for at least 30 seconds. Use the session average as your number. Peaks from a door or a cough are real, but they are not the level of the room.
- Turn on A-weighting when comparing against a limit. Noise ordinances, NIOSH and OSHA all write their numbers in dB(A). The button under the readout applies an approximation of that filter.
- Repeat at the same spot and time. Three readings on three days say more than one. Note anything unusual, such as a window open or traffic diverted.
- Know the rule you are measuring against. A reading is only useful next to the limit that applies. The noise ordinance guide quotes the codes for 36 US cities, and the quiet hours guide covers apartments.
Save report: documenting what you measured
After you press Stop, the Save report (CSV) button downloads your session: the time it was saved, duration, weighting, calibration trim, minimum, average and maximum, the NIOSH exposure verdict, the ±10 dB disclaimer, and every sampled reading at a tenth of a second. Print report gives the same summary as a page. Nothing leaves your device until you choose to save it. Kept with the date and time, a set of these files is a noise log, which is what a property manager, mediator or code officer will ask for before anything else. The FAQ on measuring neighbor noise for a complaint has a log template, and how to file a noise complaint lists where the log goes in each city.
Your privacy
Everything happens locally in your browser tab. The audio stream is analysed in memory and discarded — there is no recording, no upload, no server. Close the tab and it is gone.
Understanding decibels and sound measurement
Decibels are a logarithmic scale, which is why the numbers feel unintuitive. 0 dB SPL is the quietest sound a young ear can detect, a pressure of 20 micropascals. Every 10 dB is ten times the sound energy and roughly twice as loud to the ear, so 80 dB is not a third louder than 60 dB but a hundred times the energy. Every 3 dB doubles the energy, which is why NIOSH halves the safe time for each 3 dB step. Two identical sources together read 3 dB more than one, not twice the number. Distance works the same way in reverse: a point source loses about 6 dB each time you double your distance from it, which the sound distance calculator works out for any level.
The meter reports sound pressure level (SPL). With A-weighting on it approximates dB(A) rather than dB(C), trimming the deep bass and high treble the ear discounts. Frequency in hertz is a separate axis from level, covered in hertz versus decibels; the optional spectrum view under the readout shows both at once.
When you need a real sound level meter
Anything with legal or occupational weight needs an instrument built to IEC 61672: a class 2 meter for general and environmental work, class 1 for laboratory-grade precision, checked against an acoustic calibrator before and after each measurement. That is what a code enforcement officer brings, what an OSHA noise survey uses, and what a court will accept. A browser meter is the screening step before that: it tells you whether a problem is worth an official measurement, and it costs nothing to check. We do not sell or recommend hardware; the accuracy page explains the classes and the error envelope of a phone in more detail.
Health impact of noise
Hearing damage from noise is cumulative and permanent: the hair cells in the inner ear that convert vibration to nerve signals do not grow back. The EPA puts the ceiling for everyday sound at 70 dB, and NIOSH sets the working limit at 85 dB(A) over 8 hours. The World Health Organization recommends keeping road traffic noise below 53 dB Lden across the day and 45 dB Lnight at night to protect sleep, and estimates that over a billion young people risk hearing loss from unsafe listening, mostly through headphones and venues. Chronic exposure well below the damage threshold is still linked to disturbed sleep and cardiovascular strain, which is why cities map it: noise pollution explained covers the evidence, and the US city noise ranking and European ranking show where exposure is highest.
Reference points
30 dB is a soft whisper, 60 dB a normal conversation, 85 dB the level at which NIOSH says sustained exposure starts damaging hearing, and 110 dB a loud concert. If you are worried that noise around you has already taken a toll, the free online hearing test checks your hearing with a tone sweep in the browser, no sign-up, and the hearing age test finds the highest pitch you can still hear. The full decibel levels chart lists 40+ common sounds with sourced ranges, and the city sound map ranks the estimated noise levels of 50 major cities. To check the other side of the equation, the speaker test tones generator plays a pure tone from 20 Hz to 20 kHz so you can hear what your speakers and your ears actually reproduce. Teachers can use the classroom noise meter, the same engine with a threshold the whole room can see.
On your phone? Decibel Shield for iOS adds adjustable calibration, measurement history, Apple Health sync, and exposure alerts. Scan to open the App Store.
Common questions
How accurate is an online decibel meter?
Browser and phone microphones are not calibrated, so treat readings as estimates within roughly ±10 dB. They are good for comparing situations — is the bar louder than the street? — not for legal or occupational measurements, which require a calibrated SPL meter.
What decibel level is dangerous?
NIOSH sets the workplace recommended exposure limit at 85 dB(A) averaged over 8 hours; every 3 dB increase halves the safe time. Above roughly 100 dB, damage is possible in minutes. 120 dB and up risks immediate injury.
Why do decibel apps show different readings?
Different microphones, different weighting filters, different averaging windows, and different calibration offsets. Two uncalibrated devices can easily disagree by 5–10 dB on the same sound. Hardware calibration, like dedicated meters use, is what closes the gap.
Can your iPhone measure decibels accurately?
Yes, within limits. NIOSH researchers found that the best iOS sound meter apps read within about ±2 dB of professional reference meters in lab tests — good enough for awareness and exposure screening. Phone microphones still struggle with very loud peaks and are not a legal substitute for a calibrated SPL meter.
What does dB(A) mean?
dB(A) is a decibel reading filtered to match human hearing, which is less sensitive to very low and very high frequencies. The A-weighting curve trims those extremes — a 60 Hz hum measures far lower in dB(A) than its raw level. Nearly all noise regulations and exposure limits are written in dB(A).
How loud is too loud for headphones?
Keep headphones at or below about 80 dB(A) for up to 40 hours a week — the WHO’s safe-listening allowance. Most phones can exceed 100 dB at maximum volume, where safe time is minutes. A practical rule: if someone beside you can hear your music, it’s too loud.
Can I measure noise from my neighbors for a complaint?
Yes — phone or browser readings are useful for documenting a pattern, but they’re rarely accepted as formal evidence because the devices aren’t calibrated. Log dates, times and levels consistently, check your local noise ordinance’s limits, and request an official measurement if escalation is needed.