About DecibelPro

DecibelPro is a sound level meter that runs in your web browser. It uses your device's microphone to compute A-weighted sound pressure levels in real time, tracks the statistics that occupational noise standards are written in, and shows a waveform and frequency spectrum alongside the number. It requires no download and no account, and the audio never leaves your device.

Around the meter sits reference material that a bare number needs to be useful: a decibel chart of common sounds, an OSHA and NIOSH dose calculator, guides to workplace exposure limits, and noise ordinances for US metros.

Most people who need a decibel reading need it once, right now, and for a specific reason: a workshop that seems too loud, a neighbour who starts at eleven, a classroom that will not settle, a room that is ruining a recording. Buying an instrument is disproportionate to the question, and installing an app to answer it once is friction that stops people finding out.

A browser can answer that question in about ten seconds. What it cannot do is answer it to a standard that would survive a legal challenge, and we think being clear about which of those you are getting is the more useful contribution.

Exposure limits, exchange rates, and health effects come from primary sources — OSHA's published standards, the NIOSH criteria document, CDC and NIDCD material on noise-induced hearing loss, and WHO guidance — rather than from other websites. Those sources are linked directly wherever a figure is quoted, and collected on the references page, so you can check the number rather than trust it.

Where a figure is computed rather than quoted, we say so. The exposure tables, for instance, are calculated from the NIOSH 3 dB and OSHA 5 dB exchange-rate formulas so that intermediate levels can be included, rather than transcribed from the abbreviated tables printed in the standards. The noise ordinance pages are read from each municipality's own code.

When we get something wrong and someone tells us, we fix it and note it in the changelog. There is a real example there: the meter once could not report a level above 60 dBA because of a signal-processing mistake, which made the OSHA panel read "OK" in every room. That is documented rather than buried.

This meter is not certified to IEC 61672, is not a Class 1 or Class 2 instrument, and has no calibration traceability. It should not be used for compliance documentation, enforcement, or litigation. We publish the full measurement methodology and an accuracy page that gives ranges by device type instead of a single flattering number, including the cases where the range is wide and the fact that we have not yet published our own laboratory comparison.

Three ways, all of them visible on the site. The meter is free and stays free. Some pages carry Amazon Associates links to hardware, and we may earn a commission on purchases made through them — disclosed on the pages that carry them. And there is an optional paid Pro tier for people who need to document readings repeatedly, which adds timed sessions with saved charts and PDF reports.

The commission does not decide what gets recommended. The most common honest recommendation on this site is that if your measurement has to hold up to scrutiny, you need a real instrument rather than a browser — which is advice that sends people away from the free tool and toward a purchase we may or may not earn anything on.

Corrections, questions, bug reports, and calibration comparison data are all welcome at [email protected]. If you have a calibrated meter and are willing to run a comparison, the accuracy page describes what would be most useful.