Noise Pollution Meter

This tool measures the RMS energy of your microphone signal every animation frame and smooths it over about a second (a “slow” meter response), behaving like a browser-based noise level meter. The raw result is in dBFS — decibels relative to digital full scale, where 0 is the loudest the system can capture and quieter sounds are negative. A web browser receives only a normalised digital signal: it has no idea how sensitive your particular mic is, how far the source is, or what gain the OS applied. So out of the box this is a relative measurement, honest for comparisons (louder vs quieter, before vs after) but not an absolute environmental decibel value.

To show a meaningful dB SPL number you must calibrate. Stand a real sound-level meter or a calibrated phone app next to your mic, read its current level, and type that into the calibration box while this tool is running. The tool stores a single offset (known − measured dBFS) under the shared key fd-noise-cal, so every Noise tool on the site reuses it — calibrate once, and the whole category gives the same estimate. Even then the figure is an uncalibrated estimate: it drifts with distance, mic position and the spectrum of the sound, and it is never a substitute for a Type 1/2 meter. It is also unweighted (flat / Z-weighted) — the tool does not apply the A-weighting curve, so it only matches an A-weighted meter when the source spectrum resembles the calibration spectrum, and it over-reads low-frequency-dominated sources (HVAC rumble, distant traffic) relative to a true dB(A) reading.

Once calibrated, the colour traffic light compares your estimated level against published guidance to flag hearing risk: green below about 55 dB(A) (the WHO daytime outdoor community-noise guideline), amber up to 70 dB(A), orange up to 85 dB(A) (around the EPA’s 70 dB(A) 24-hour average to prevent measurable hearing loss), and red at or above 85 dB(A), the NIOSH occupational limit. The recommended max exposure applies the NIOSH rule of 8 hours at 85 dB(A) with a 3 dB exchange rate (every extra 3 dB halves the safe time). If you know both the average level and the duration of an exposure, you can calculate a more detailed daily noise dose using the noise exposure calculator. These thresholds are real published values; the comparison is for personal orientation, not a legal or medical judgement.

One physical caveat: consumer mics roll off at the frequency extremes and generally cannot capture true infrasound (<20 Hz) or deep sub-bass, so low-frequency sources (HVAC rumble, distant traffic, machinery) may read lower than they feel. Spectral shape and before/after comparisons with the same mic and setup remain trustworthy even uncalibrated. If you want to see exactly which frequencies dominate the noise rather than just the overall level, try the noise spectrum analyzer alongside this tool.

The session statistics — Leq, Lmax and L90 — each serve a different purpose. Leq (equivalent continuous level) is an energy average over the whole session: the single level that would deliver the same total acoustic energy as the fluctuating noise. Lmax is the loudest instantaneous peak captured. L90 is the level exceeded for 90% of the session — a standard proxy for the steady background noise floor since it filters out brief spikes. Environmental noise regulations typically cite Leq or L10 (the level exceeded 10% of the time); L90 is most useful for characterising the quiet baseline. All three are shown here as relative metrics and, once calibrated, as estimated dB SPL.

dBFS (decibels relative to full scale) is what an uncalibrated browser microphone reports. The scale runs from 0 (the loudest the digital system can represent) downward into negative values, so a quiet room might read around −40 dBFS. It is a relative level — it tells you nothing about real-world loudness until you anchor it to a known reference. That is exactly what this tool shows before calibration.

dB SPL (sound pressure level) is an absolute physical quantity referenced to 20 micropascals — the threshold of human hearing. Measuring it correctly requires a calibrated sound-level meter, not a consumer microphone. dBA (A-weighted dB SPL) adds a frequency-shaping curve that de-emphasises low bass and very high frequencies to better match how humans perceive loudness. Every OSHA, NIOSH, WHO and EPA noise limit is expressed in dBA. This tool's readings are unweighted dBFS — not dBA and not certified dB SPL. If you need to calculate your cumulative noise dose from a level and duration, use the noise exposure calculator.