How accurate is this online decibel meter?

On a modern smartphone or laptop, expect within about 3 to 5 dB of a certified sound level meter in the 50 to 90 dB range. That is accurate enough for everyday questions (is this room too loud, is this appliance noisy) but not for compliance, legal, or engineering work. For that, use an IEC 61672 class meter. For iPhone users, the Noise app on Apple Watch is factory calibrated and more trustworthy than any browser or third-party app.

Does the tool record my audio?

No. The microphone stream is processed live in your browser to calculate sound level. Nothing is saved, transmitted, or uploaded. The stream is released the moment you tap Stop or leave the page. You can verify this by checking the browser dev tools network tab while the tool runs.

Why does it show negative or 0 dB when I first start?

The first few frames sample very quiet audio while the microphone warms up, which the calibration formula can render as very low or negative. Give it 1 to 2 seconds and the reading stabilises. If it stays stuck at 0 or negative, the browser may have muted the mic or applied noise gating you cannot control.

Why is my iPhone reading lower than my Apple Watch Noise app?

Apple Watch has a purpose-built, factory-calibrated microphone for sound level measurement. iPhone microphones are tuned for voice calls, with roll-off outside the speech band and manufacturing variation between units. Expect a browser-based reading on iPhone to run a few dB below the Watch. If both agree to within 5 dB, that is the expected result.

Can I use this to measure noisy neighbours for a legal complaint?

No. Legal noise complaints require a certified meter with a documented calibration certificate and a proper measurement protocol (time weighting, distance from source, integration period). A browser tool is fine for personal awareness but will not stand up in any regulatory or legal context. Contact your local council or environmental health department, which typically has calibrated equipment.

Does it work on iPhone Safari?

Yes, on iOS 14.3 and later. Safari requires HTTPS and a user tap to start the audio context, both of which are handled by the Start button. If the meter shows no movement, check Settings > Safari > Microphone and confirm access is set to Ask or Allow for this site.

What is dB SPL and how is it different from dBFS?

dB SPL (Sound Pressure Level) is a measurement of real acoustic energy in air, referenced to 20 micropascals (the threshold of human hearing). dBFS (dB Full Scale) is a digital-audio measurement referenced to the loudest signal a digital system can encode without clipping. 0 dBFS is digital maximum, and everything else is negative. This meter converts dBFS to approximate dB SPL by applying a calibration offset.

Which browsers work with the decibel meter?

Chrome, Firefox, Safari, and Edge on desktop, plus Safari on iOS 14.3+ and Chrome on Android. The site must be served over HTTPS for microphone access to work (spyhearing.com is HTTPS). Internet Explorer and older browsers are not supported because they lack the Web Audio API.

Decibel Meter Online

Measure ambient sound in decibels using your device microphone. Free, no signup, works in any modern browser on iPhone, Android, Mac, and Windows.

dB SPL (approx.)

Idle

Min--

Avg--

Max--

Tap Start and allow microphone access. Nothing is recorded or uploaded.

This tool measures how loud your surroundings are. If the opposite is the problem, sound too quiet to hear clearly, Spy Hearing amplifies live audio on iPhone up to 16x through any headphones.

Try Spy Hearing on iPhone

How to use it

Tap Start measuring and allow microphone access when prompted.
Hold your phone or laptop where your ear normally sits.
Let it run for at least 10 seconds so the average settles.
Read the current dB level, plus min, average, and max in the stats row.
Tap Stop to release the microphone.

What decibel levels mean

Sound levels are logarithmic. Every 10 dB increase is roughly a doubling of perceived loudness, and every 3 dB increase is a doubling of acoustic energy. Rough reference points:

dB SPL	Example	Effect
0 to 20	Anechoic chamber, rustling leaves	Barely audible
30	Whisper, quiet library	Very quiet
40 to 50	Quiet office, refrigerator hum	Comfortable
60	Normal conversation, background music	Comfortable
70	Vacuum cleaner, busy restaurant	Noticeable, not harmful
80	City traffic, alarm clock	Prolonged exposure starts to matter
85	Heavy traffic from inside car, gas mower	OSHA action level; hearing protection recommended for 8+ hours
90	Blender, subway train	Hearing damage possible after ~2 hours
100	Motorcycle, hand drill	Damage in ~15 minutes without protection
110	Rock concert, chainsaw	Damage in under 2 minutes
120+	Ambulance siren, jet takeoff at 100 ft	Immediate risk, pain threshold

Levels are based on CDC / NIOSH exposure guidelines. If you regularly measure 85 dB or more where you spend time, hearing protection is a genuine consideration. Plug the number into our safe listening time calculator to see how long that exposure is safe per NIOSH guidelines, or take our hearing age test to check whether past noise exposure has already affected your top-of-range hearing.

Is a browser decibel meter accurate?

Honest answer: not laboratory-accurate. A certified Type 1 or Type 2 sound level meter costs $100 to $2000 and uses a calibrated pressure-response microphone with a known sensitivity. Your phone or laptop microphone was designed for voice calls, not measurement, and its sensitivity varies by device.

This tool applies a general calibration offset that puts most modern smartphones and laptops within roughly ±3 to 5 dB of a calibrated meter in the 50 to 90 dB range. That is close enough to answer questions like "is this room noisy enough to damage my hearing over time?" but not close enough for compliance work or acoustic engineering.

For higher accuracy on iPhone, the built-in Noise app on Apple Watch is factory-calibrated and reasonably trustworthy. On Android, Google's Sound Amplifier shows ambient dB with similar calibration. For workplace or legal use, get a real IEC 61672 class meter.

Why we disable audio processing

By default, browsers apply echo cancellation, noise suppression, and automatic gain control to microphone input. Automatic gain control is the big problem: it silently boosts quiet sounds and cuts loud ones, so a raw browser mic feed would lie about the actual sound level. This tool requests the microphone with all three of those disabled so the reading reflects real acoustic level as closely as the hardware allows.

Common uses

Check if a room is too loud for a meeting or recording. Above 45 dB ambient, voice recordings pick up the background noise.
Test appliance noise. HVAC systems, dishwashers, fans, and PC cooling. Measure at 1 metre.
Check restaurant or gym noise. Discreetly measure whether a venue is above the 80 dB level where prolonged exposure matters.
Verify hearing protection. Measure a loud environment before and after putting earplugs in to see the real attenuation.
Track sleep environment. Above 40 dB is where noise starts to affect sleep quality for most people.

Frequently asked questions

How accurate is this online decibel meter?: On a modern smartphone or laptop, expect within about 3 to 5 dB of a certified sound level meter in the 50 to 90 dB range. That is accurate enough for everyday questions (is this room too loud, is this appliance noisy) but not for compliance, legal, or engineering work. For that, use an IEC 61672 class meter. For iPhone users, the Noise app on Apple Watch is factory calibrated and more trustworthy than any browser or third-party app.
Does the tool record my audio?: No. The microphone stream is processed live in your browser to calculate sound level. Nothing is saved, transmitted, or uploaded. The stream is released the moment you tap Stop or leave the page. You can verify this by checking the browser dev tools network tab while the tool runs.
Why does it show negative or 0 dB when I first start?: The first few frames sample very quiet audio while the microphone warms up, which the calibration formula can render as very low or negative. Give it 1 to 2 seconds and the reading stabilises. If it stays stuck at 0 or negative, the browser may have muted the mic or applied noise gating you cannot control.
Why is my iPhone reading lower than my Apple Watch Noise app?: Apple Watch has a purpose-built, factory-calibrated microphone for sound level measurement. iPhone microphones are tuned for voice calls, with roll-off outside the speech band and manufacturing variation between units. Expect a browser-based reading on iPhone to run a few dB below the Watch. If both agree to within 5 dB, that is the expected result.
Can I use this to measure noisy neighbours for a legal complaint?: No. Legal noise complaints require a certified meter with a documented calibration certificate and a proper measurement protocol (time weighting, distance from source, integration period). A browser tool is fine for personal awareness but will not stand up in any regulatory or legal context. Contact your local council or environmental health department, which typically has calibrated equipment.
Does it work on iPhone Safari?: Yes, on iOS 14.3 and later. Safari requires HTTPS and a user tap to start the audio context, both of which are handled by the Start button. If the meter shows no movement, check Settings > Safari > Microphone and confirm access is set to Ask or Allow for this site.
What is dB SPL and how is it different from dBFS?: dB SPL (Sound Pressure Level) is a measurement of real acoustic energy in air, referenced to 20 micropascals (the threshold of human hearing). dBFS (dB Full Scale) is a digital-audio measurement referenced to the loudest signal a digital system can encode without clipping. 0 dBFS is digital maximum, and everything else is negative. This meter converts dBFS to approximate dB SPL by applying a calibration offset.
Which browsers work with the decibel meter?: Chrome, Firefox, Safari, and Edge on desktop, plus Safari on iOS 14.3+ and Chrome on Android. The site must be served over HTTPS for microphone access to work (spyhearing.com is HTTPS). Internet Explorer and older browsers are not supported because they lack the Web Audio API.