Sleep Environment Noise Checker
Hold your phone or laptop where your head rests at night and measure your bedroom’s noise level from the microphone in real time. The tool compares it against published WHO night-noise guidance, tells you whether the noise is low-frequency rumble (traffic, machinery) or mid/high-frequency sound (neighbours, appliances, fans), and suggests a masking approach.
ℹ This is an uncalibrated estimate, not a certified sound-level meter. A browser/phone mic isn’t calibrated, rolls off at the frequency extremes, and generally cannot capture true infrasound or deep sub-bass. Until you calibrate it against a real meter the level is shown as dBFS (relative, ≤ 0); the dB SPL figure is only an estimate. It is not a substitute for a Type 1/2 meter and is not valid as legal, complaint or compliance evidence. The most trustworthy outputs here are the noise character (low vs high frequency) and before/after comparisons with the same mic and setup — those don’t depend on calibration. Nothing is recorded or uploaded.
Microphone
SPL calibration (shared across noise tools)
Night-noise level
WHO Night Noise Guidelines for Europe (2009) suggest an annual Lnight,outside of 40 dB(A) and a long-term target of 30 dB(A). The bands below mirror common indoor sleep guidance; they apply only once you have calibrated for dB SPL. Note that the tool measures an unweighted broadband level, whereas the WHO figures are dB(A), so a rumble-heavy bedroom reads higher unweighted than its true dB(A) — treat the comparison as a rough guide.
Noise character
Masking suggestion will appear here once measuring. As a rule of thumb: steady broadband masking from a white, pink or brown noise source can cover intermittent disturbances by reducing the contrast between quiet and loud moments — brown/pink suit low rumble, white/pink suit higher chatter.
How It Works
When you press Start, the tool requests that your microphone’s automatic gain, noise suppression and echo cancellation be switched off (these would distort any noise measurement); if your OS or browser forces them on anyway, treat the reading as unreliable. It then continuously reads the raw waveform. From each short frame it computes the RMS energy and converts it to dBFS — decibels relative to digital full scale, where 0 is the loudest the system can capture and quieter sounds are negative. dBFS is genuinely meaningful as a relative level: it lets you compare a window open versus closed, a fan on versus off, or tonight versus last night with the same device and placement.
A browser cannot know your microphone’s real-world sensitivity, so it cannot turn dBFS into a true dB SPL on its own. That is what the calibration control is for. While the tool is measuring, read the level on a calibrated sound-level meter or a reputable calibrated phone app, type that number in, and press Set calibration. The tool stores the offset (known SPL − current dBFS) in your browser under the shared key fd-noise-cal, so every noise tool on the site — this one, the environmental monitor, the pollution meter — uses the same calibration. Calibrate once and your dB SPL estimates carry over. The offset never leaves your device.
Alongside the level, an FFT splits the sound into low (20–200 Hz), mid (200 Hz–2 kHz) and high (2–16 kHz) energy. Low-frequency dominance points to traffic rumble, HVAC or machinery — hard to block, best tackled with brown/pink masking and sealing gaps. Mid/high dominance points to voices, TVs, fans and appliances — easier to mask with white or pink noise. Because consumer mics roll off below roughly 50–100 Hz, the very deepest rumble and any true infrasound (<20 Hz) will read low or be missed entirely; the spectral shape is still a reliable guide to what kind of noise you are dealing with. The level series also yields Leq (the equivalent continuous level, energy-averaged), L90 (the level exceeded 90% of the time — a good proxy for the steady background), and Lmax/Lmin. These are valid relative metrics whether or not you have calibrated.
The verdict bands echo widely cited sleep guidance: the WHO Night Noise Guidelines for Europe (2009) recommend an annual night-outside level (Lnight,outside) of 40 dB(A) with a long-term target of 30 dB(A), below which there are no substantiated effects on sleep. As an indoor rule of thumb the tool treats roughly <30 as ideal, 30–40 as acceptable, and >40 as likely disruptive. Those WHO numbers are real published values in dB(A), but the tool computes an unweighted (Z-weighted) broadband level — it applies no A-weighting filter — so its calibrated figure is a dB SPL unweighted estimate, not dB(A). Because A-weighting cuts the low end heavily, a bedroom dominated by traffic or HVAC rumble will read higher unweighted than its true dB(A); treat the verdict as a rough guide. The comparison is for guidance only and is only meaningful once you have calibrated for dB SPL — before that the tool shows the relative dBFS level and withholds the verdict rather than inventing a number.