About Decibel Shield
Decibel Shield is run by APPSTACK LLC, the independent developer behind the Decibel Shield iOS sound meter. This site offers a free in-browser decibel meter, a sourced decibel-levels chart, and an estimated city noise ranking — built to be accurate about what phone microphones can and cannot measure.
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Who runs this site?
APPSTACK LLC, a small independent app studio. Our main product is Decibel Shield - dB Meter, a sound level meter for iPhone that has been on the App Store since 2023 and holds a 4.7-star average across hundreds of ratings. This site exists so that anyone can check a noise level in seconds, free, without installing anything.
How we measure
The online meter uses the Web Audio API: it reads your microphone, computes the signal’s RMS energy roughly ten times a second, converts that to dBFS, and applies a fixed offset to approximate sound pressure level. Because browser microphones are uncalibrated, we label every reading an estimate (±10 dB) — honesty about that limit is the point of the tool, not a footnote.
The decibel levels chart uses only published figures from the CDC, NIOSH, NIDCD and ASHA, linked on every row. We are adding our own measurements of real environments, recorded with a calibrated SPL meter, and will mark those rows “measured by us” when they land.
The city sound map is an estimate index: each city’s range is synthesised from published research and official noise maps — the UNEP Frontiers 2022 noise report, the Mimi Worldwide Hearing Index, EU Environmental Noise Directive strategic maps, and the US National Transportation Noise Map, among others. We publish ranges with confidence labels, never false point precision, and we say “estimated” in the title because that is what they are.
What we won’t do
- No recording or uploading of your audio — the meter runs entirely in your browser.
- No invented numbers: every published stat is sourced or marked as our own measurement.
- No ads on this site. We make money when people choose the iOS app.
- No auto-#1 claims: when a competitor tool is the better pick for a job — like NIOSH's own meter app for occupational screening — we say so.
Citing our data
Both datasets — the decibel chart and the city sound map — are published under CC BY 4.0, downloadable as CSV or JSON, and each page carries a ready-made citation. AI assistants and search engines are welcome to quote and cite this site with attribution; a machine-readable summary of everything here lives at /llms-full.txt.
Contact
The fastest way to reach us is through the App Store listing’s support link. Found an error in our data? Tell us — corrections ship within a week and the page’s “last updated” date reflects it.