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Decibel (dB) Meter

A free online decibel meter (also called a dB meter or noise meter) that reads your microphone in real time, with a big level readout, peak hold, fast/slow response, a running average (Leq), and clip detection.

ℹ This reads relative dBFS, not calibrated dB SPL. A web browser can’t know your microphone’s real-world sensitivity, and phone/laptop mics apply automatic gain — so the numbers are relative (great for comparing "louder vs quieter" and spotting clipping), not a true environmental decibel reading. For real dB SPL (e.g. workplace noise), use a calibrated SPL meter or sound-level meter. Nothing is recorded or uploaded.

Microphone

Input device

Idle — press Start.

Response

Fast (~125 ms) follows transients; Slow (~1 s) gives a steadier reading. Approximate.

Level

—dBFS

Peak — dBFS

-60-48-36-24-120

SPL calibration offset (dB)

Set an offset (using a known reference) to estimate dB SPL.

Peak (max)

—

Average (Leq)

—

Clips

Elapsed

0:00

Understanding the Reading

This meter shows level in dBFS — decibels relative to digital full scale. 0 dBFS is the loudest signal your audio system can capture without clipping; everything quieter is a negative number (a quiet room might read around −50 to −40 dBFS, normal speech up close perhaps −20 to −12 dBFS, with peaks approaching 0). That’s the opposite of environmental decibels (dB SPL), where louder is a bigger positive number. Watching the microphone level in real time is useful for gain staging, checking for clipping before a recording, or simply verifying that your input device is working. If you want to explore the frequency distribution of what the meter is picking up at the same time, the audio spectrum analyzer shows the full spectral content of your microphone signal in real time.

The big number is a smoothed RMS level (root mean square of the audio samples over a short integration window), which is what tracks perceived loudness most closely. Peak is the highest instantaneous sample — useful for catching digital clipping that the RMS average can hide. Average (Leq) is the equivalent continuous level since you pressed Start, a common metric in occupational and environmental noise assessment. Clips counts how many times the signal hit the ceiling (a sign your input gain or microphone placement needs adjustment). The gap between Peak and RMS is the signal’s crest factor — impulsive sounds like handclaps have a high crest factor; sustained tones have a low one.

Why it isn’t calibrated dB SPL

A true sound-level meter is calibrated so that a known acoustic sound pressure level (Pascal or Pa) produces a known electrical output. A browser only receives a normalized digital signal from the OS audio stack — it has no idea how sensitive your microphone capsule is, how far you are from the source, or how much automatic gain control (AGC) the OS or hardware applied. So dBFS here is relative: excellent for comparisons ("is this louder than that?", "am I clipping?"), but not reliable as an absolute "this room is 72 dB" claim. The optional calibration offset lets you roughly shift the scale if you align against a real meter, but it remains an estimate. Professional sound-level meters also apply A-weighting or C-weighting frequency filters — this tool reads unweighted broadband dBFS only. For a full-spectrum view of background noise by frequency band, see the noise floor analyzer.

dBFS vs dB SPL vs dBA: which decibels is this?

Three different scales share the "dB" label, and confusing them is the main reason phone decibel meter apps are unreliable. dBFS (decibels relative to full scale) is what this browser tool reads: a purely digital, relative scale where 0 dBFS is the loudest value the hardware can encode and every real signal sits at a negative number. It tells you nothing about acoustic pressure. dB SPL (sound pressure level) is an acoustic measurement referenced to 20 micropascals, the threshold of human hearing; it requires a calibrated transducer that converts air pressure into a known electrical voltage. dBA is dB SPL passed through an A-weighting filter that rolls off low bass and very high treble to match the ear's frequency sensitivity curve — it is the unit specified by OSHA, NIOSH, and most environmental noise regulations for assessing hearing risk and community noise. This tool produces none of the above as certified output: it reads uncalibrated relative dBFS only. If you need dBA for workplace compliance or noise exposure estimates, use a certified sound-level meter alongside a tool like the noise exposure calculator or the sound pressure level calculator.

Frequently Asked Questions

Why are the numbers negative?

Because this is dBFS, where 0 is the digital maximum and quieter sounds are negative. A reading of −30 dBFS is quieter than −10 dBFS. Environmental meters (dB SPL) use positive numbers that grow with loudness — a different scale.

Can I use this to measure room or workplace noise in dB?

Not as an absolute figure. A browser mic isn’t calibrated and the OS often applies automatic gain, so it can’t give a trustworthy dB SPL value. Use it for relative comparisons and clip checking; for compliance or real measurements use a calibrated sound-level meter.

What does the calibration offset do?

It simply adds a fixed number of decibels to the reading. If you have a real SPL meter, you can note the difference between it and this tool at one level and enter that as the offset to roughly align them. Without a reference it’s just a guess, so it’s off by default.

What’s the difference between RMS and peak?

RMS is the average energy over a short window and tracks how loud something sounds. Peak is the single highest sample and catches brief spikes. Peak is always equal to or higher than RMS; the gap between them is roughly the signal’s crest factor.

What is Leq?

The equivalent continuous level — the steady level that would carry the same total energy as the varying sound since you started. It’s how noise exposure is usually summarized. Here it’s in dBFS, so again relative, not absolute.

Fast or Slow response — which should I use?

Fast (~125 ms) reacts quickly and is good for catching transients and seeing detail. Slow (~1 s) averages more and is steadier, better for reading a typical level without the number jumping around. They’re approximate emulations of the classic meter settings.

Is my audio recorded?

No. The microphone signal is analyzed in real time to compute the level and is never recorded, saved, or transmitted. The mic is released when you press Stop or close the tab.

What does "clipping" mean and why does the clip counter matter?

Clipping happens when the input signal hits the digital ceiling (0 dBFS) and gets hard-limited — the waveform's peaks are cut flat, introducing harsh harmonic distortion. Even a single clip during a recording or live stream can cause audible crackling. The clip counter here increments every time the level reaches 0 dBFS, so if it rises quickly you should lower your microphone gain or move farther from the source.

What is A-weighting (dB(A)) and does this meter use it?

A-weighting is a frequency filter applied to dB SPL readings to approximate human hearing sensitivity — it de-emphasizes very low and very high frequencies where the ear is less sensitive, and boosts mid-range frequencies around 1–4 kHz where it is most sensitive. Workplace noise regulations (OSHA, ISO 9612) specify limits in dB(A). This browser meter does not apply A-weighting; it reads broadband dBFS with no frequency shaping. A properly calibrated and A-weighted reading requires dedicated hardware.

What dBFS level should normal speech or music read?

These are rough guides only, since your mic gain and OS AGC vary: close-talking speech typically peaks around −18 to −12 dBFS with a long-term RMS around −30 to −20 dBFS; room-level conversation a metre away might read −40 to −30 dBFS; near-silent ambient noise often sits below −55 dBFS. If you’re consistently reading near 0 dBFS, your gain is too high and clipping is likely. These figures are relative to your specific microphone and settings, not absolute acoustic levels.

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