Noise Level Logger
This free noise level logger records your microphone level over time with timestamps. You get a live dB chart, a configurable sample interval, running statistics (Leq, L90, Lmax and Lmin), one-click CSV export, and saved sessions you can compare before vs after a change.
ℹ This is an uncalibrated estimate, not a certified sound-level meter. A web browser can’t know your microphone’s real sensitivity, so the log is in dBFS (relative to digital full scale). It is great for tracking change over time and comparing before/after with the same setup, but it is not a true dB SPL reading and the CSV is indicative documentation only — not valid as legal, complaint or compliance evidence. For that, use a calibrated Type 1/2 meter. Automatic gain control and noise suppression are requested off (a reading is meaningless otherwise). Nothing is recorded or uploaded; sessions stay in this browser.
Microphone & logging
Each logged point is the energy-averaged level (Leq) over that interval.
Consent: the tool only listens after you press Start and only to compute levels. Audio is never recorded or sent anywhere.
Calibration (optional, shared)
Not calibrated.
Live level
Level history (most recent samples) — dBFS over time
Saved sessions & before/after comparison
Sessions are stored only in this browser (localStorage). Use them to compare, for example, a room before and after you turned off a fan.
How It Works
Press Start logging and grant microphone access. The tool reads the live waveform many times per second and computes the RMS level in dBFS — decibels relative to digital full scale, where 0 dBFS is the loudest signal the system can capture without clipping and quieter sounds are negative numbers. At every sample interval you choose (1, 5, 10, 30 or 60 seconds), it stores one point: the energy-averaged level over that interval, stamped with the current clock time from your device. This time-series approach mirrors the sound level logging methodology used in professional environmental noise surveys, where a data-logger writes a new environmental noise log entry at a fixed interval over hours or days.
The live chart plots the most recent points so the canvas stays light no matter how long you record. Functioning as an in-browser Leq logger, the tool continuously updates four classic noise descriptors: Leq (the equivalent continuous level — the steady level carrying the same total energy as the varying sound), L90 (the level exceeded 90% of the time, a good proxy for the background noise floor), and Lmax / Lmin (the loudest and quietest logged samples). All are computed on the dBFS series, so they are valid as relative metrics. L90 in particular is widely used in neighbourhood noise assessment frameworks to characterise the residual or ambient level before a specific source is present. If you also need to identify what kind of noise is causing an elevated level, pair this logger with the noise frequency analyzer to match spectral signatures.
Because a browser microphone is uncalibrated, these numbers are not true dB SPL on their own. If you have a real sound-level meter or a calibrated phone app, read the current level on it, type that value into Calibration, and the tool stores an offset = known SPL − current dBFS. That offset is saved under a shared key (fd-noise-cal) so every noise tool on this site uses the same calibration — calibrate once and it carries over. SPL figures shown after that are clearly labelled estimates and reflect a single-point calibration, which is a reasonable approximation for mid-level signals but will be less accurate at extremes of the dynamic range.
Press Export CSV to download your noise data as a CSV file (timestamp and level per row, plus a header noting the interval, calibration and summary metrics) as a local file. Press Save session to keep a snapshot in this browser, then pick any two saved sessions to see the before/after difference in Leq, L90, Lmax and Lmin. Measured with the same microphone and setup, those differences are calibration-independent and genuinely meaningful — useful for checking whether soundproofing improvements, window sealing, or moving a noise source actually changed your environment. For a complementary live view without the logging focus, try the decibel meter for instant peak-hold and clip detection.
Frequently Asked Questions
Is this a real sound-level meter I can use for noise complaints?
No. This is an uncalibrated estimate from a consumer microphone. It is excellent for tracking how levels change over time and for before/after comparisons with the same setup, but it is not a certified Type 1/2 sound-level meter and the readings (and the CSV) are not valid as legal, complaint or compliance evidence. For that you need a calibrated meter operated to the relevant standard.
Why are the levels shown in dBFS, and why are they negative?
dBFS means decibels relative to digital full scale: 0 dBFS is the digital maximum and everything quieter is negative. A quiet room might log around −60 to −45 dBFS and a loud room far higher. This is the opposite of environmental dB SPL, where louder is a bigger positive number. dBFS is the honest thing a browser can report, because it has no way to know your mic’s real-world sensitivity.
How do I get an estimated dB SPL, and what does calibration do?
Read the current level on a real sound-level meter or a calibrated phone app, type that number into the calibration box, and press Set offset. The tool stores offset = known SPL − current dBFS and then shows estimated SPL = dBFS + offset. The offset is saved under a shared key so every noise tool on this site reuses it. It is still only a rough single-point estimate, not a true calibration across all levels and frequencies.
What do Leq, L90, Lmax and Lmin mean?
Leq is the equivalent continuous level — the steady level that carries the same total energy as the varying sound over your log. L90 is the level exceeded 90% of the time, commonly used as the residual or background level. Lmax and Lmin are the loudest and quietest logged samples. Here they are computed on the dBFS series, so they are meaningful as relative measures and as differences between sessions, not as absolute SPL.
Why must automatic gain control be off?
Automatic gain control, noise suppression and echo cancellation constantly change the signal level to make voice sound good. Any of them would make a level log meaningless, because the level you see would be the processing, not the room. This tool requests the raw microphone with all three switched off; if your system still applies processing you cannot fully disable, treat the readings with extra caution.
Is my audio or my log uploaded anywhere?
No. The microphone signal is analyzed in real time to compute levels and is never recorded or transmitted. Saved sessions and your calibration offset live only in this browser’s local storage, and the CSV is a local download. Clearing your browser data removes them. The mic is released when you press Stop or close the tab.
How long can I log continuously, and will the page slow down?
You can log for many hours without the page slowing down. The live chart only draws the most recent sample window, not the entire history, so canvas rendering time stays constant. All logged samples are kept in memory until you export or clear the session, so extremely long sessions (several days at a 1-second interval) may eventually use significant browser memory. For overnight monitoring, a 10- or 30-second interval is a good balance between data resolution and memory use.
Which sample interval should I choose?
It depends on how fast your noise changes. For short events like a noisy appliance or a door slam, use 1 second to capture the peak in Lmax. For background-level surveys — checking an office, bedroom, or outdoor garden over several hours — 10 or 30 seconds gives a smooth trend without flooding the CSV with redundant data. L90 (background level) is most meaningful when computed over at least a few minutes of data, so give any session that uses L90 as a reference at least 5–10 minutes of run time.
Can I use this to document noise from a neighbour or construction site?
You can produce a timestamped CSV log that shows how your measured levels changed over time, which can be useful for personal records or informal discussions. However, because the tool reads dBFS rather than calibrated dB SPL, the data is not valid for formal complaints or legal proceedings — those require a certified Type 1 or Type 2 sound-level meter operated to the applicable standard (e.g., ISO 1996, BS 4142). The before/after session comparison feature is most honest here: it can show a clear relative increase in level without making unsupported absolute claims.