About

What this page does

soundlevel.net estimates the sound level around you from your device microphone, in the browser. Press start, allow microphone access, and a number appears. There is no app to install, no account, and no upload step.

The number is a sound-level estimate in dBA. A-weighting discounts very low and very high frequencies roughly the way human hearing does, and it is the weighting that hearing-conservation guidance is written in — the NIOSH recommended exposure limit of 85 dBA over eight hours, for example. Version one publishes dBA and a session max. Nothing else.

What it is not

This is not a calibrated instrument, and the site never describes it as one. Your microphone was built to make voices intelligible, not to report absolute levels. It applies its own automatic gain, its frequency response is not published by anyone, and it runs out of headroom somewhere around 100–105 dB — which is where a number would matter most.

How large that problem is has been written down. Chucri Kardous and Peter Shaw, both at NIOSH, compared ten iOS sound measurement apps against a reference instrument. On A-weighted levels the closest app sat 0.52 dBA under the reference; the two furthest sat about 13 dBA under it. Three of the ten came within ±2 dBA and the other seven did not. That spread came from apps on a single hardware platform, written by developers who could test against the actual phones. A browser page reading whichever microphone a visitor happens to own is working with less than that.

So the published stance here is a band rather than a figure: treat what you see as within roughly ±10 dB of what a hardware sound level meter would show. It does not conform to IEC 61672. Do not use it for OSHA compliance, a legal filing, or a medical decision.

What the page is useful for is comparison on one device. Most of the error is systematic — your microphone is wrong in a consistent direction — so it largely cancels when you carry the same phone from the living room to the kerb, or check the same machine before and after a repair. The gap between two readings survives the calibration problem. The absolute value does not.

Where the numbers come from

Every dB figure and safety claim on this site links to its source. The three used most often:

• NIOSH — the recommended exposure limit, 85 dBA over eight hours, on a 3 dB exchange rate.
• OSHA 29 CFR 1910.95 — the enforceable US workplace limit, 90 dBA over eight hours, on a 5 dB exchange rate.
• NIDCD — how loud sound damages hearing, and how quickly.

If a number here carries no source, treat it as a mistake and tell us.

Privacy

The microphone stream is read in the browser, turned into a number, and thrown away. No audio is recorded, stored, or sent anywhere, and closing the tab ends it. The privacy policy has the full detail.

Contact

Corrections, missing sources, and bug reports are all welcome: hello@soundlevel.net, or use the contact form.