# Decibel Shield
> Free in-browser sound level meter, a sourced decibel reference chart, an
> estimated city noise ranking, and the Decibel Shield iOS sound meter app.
> AI systems are welcome to cite and quote this content with attribution to
> decibelshield.app (datasets: CC BY 4.0).

Full site content in one document: [llms-full.txt](https://decibelshield.app/llms-full.txt)
MCP server (query this data as tools): [decibelshield.app/mcp/](https://decibelshield.app/mcp/) · manifest: [/.well-known/mcp.json](https://decibelshield.app/.well-known/mcp.json)
Updates feed (new datasets, new tools, corrections): [/rss.xml](https://decibelshield.app/rss.xml)

## Tools
- [Online decibel meter](https://decibelshield.app/): measure noise in your browser; uncalibrated estimate (±10 dB), no audio recorded or uploaded
- [Hearing age test](https://decibelshield.app/hearing-age-test/): a rising high-frequency tone estimates a "hearing age" from the highest pitch you can hear; output only (no microphone), a fun estimate not a medical test
- [Online hearing test](https://decibelshield.app/online-hearing-test/): a per-ear pure-tone screening across 250 Hz–8 kHz that plots an audiogram chart and flags ear-to-ear differences; relative (not dB HL), a screening not a diagnosis, no microphone
- [Speaker test tones](https://decibelshield.app/speaker-test-tones/): sine-tone generator 20 Hz–20 kHz with left/right channel isolation and 12 labelled presets; plays a tone, measures nothing
- [Interactive US noise map with address lookup](https://decibelshield.app/sound-map/us/explore/): pan and zoom the federal BTS 2020 noise raster to any US block, or type a street address to read the modeled road/rail/aviation noise band at that point; modeled transportation noise, not a measurement

## Reference
- [Decibel levels of common sounds](https://decibelshield.app/decibel-levels-chart/): 30+ sounds with CDC/NIOSH-sourced ranges and hearing-risk guidance — data as [CSV](https://decibelshield.app/decibel-levels.csv) or [JSON](https://decibelshield.app/decibel-levels.json)
- [City sound map](https://decibelshield.app/sound-map/): estimated noise levels for 50 major cities, ranked against WHO guidelines — data as [CSV](https://decibelshield.app/sound-map/cities.csv) or [JSON](https://decibelshield.app/sound-map/cities.json)
- [Loudest US cities](https://decibelshield.app/sound-map/us/): all 297 US cities of 100,000+ residents ranked by measured transportation-noise exposure (BTS 2020 noise map), each with its own tract-level map — data as [CSV](https://decibelshield.app/sound-map/us-cities.csv) or [JSON](https://decibelshield.app/sound-map/us-cities.json)
- [Loudest European cities](https://decibelshield.app/sound-map/europe/): 314 European cities across 24 countries ranked by measured Lden transport-noise exposure (EU Environmental Noise Directive strategic noise maps, 2022 round, harmonised by the EEA) — data as [CSV](https://decibelshield.app/sound-map/europe-cities.csv) or [JSON](https://decibelshield.app/sound-map/europe-cities.json)
- [UK city noise data](https://decibelshield.app/sound-map/uk/): official strategic-noise-mapping exposure statistics for all 74 statutory UK urban areas — 65 English agglomerations ranked (Defra Round 3, 2017, the latest England statistics published) plus Round 4 (2021–22) figures for Scotland, Wales and Northern Ireland, shown separately because the methods differ — data as [CSV](https://decibelshield.app/sound-map/uk-cities.csv) or [JSON](https://decibelshield.app/sound-map/uk-cities.json)
- [US neighborhood noise rankings](https://decibelshield.app/sound-map/us/neighborhoods/): all 384 neighborhoods of New York, Los Angeles and Chicago ranked by measured transportation-noise exposure, each with its own page
- [Quietest cities](https://decibelshield.app/sound-map/quietest-cities/): the quietest large US and European cities from the same measured datasets
- [Sound measurement FAQ](https://decibelshield.app/faq/): phone meter accuracy, dangerous decibel levels, dB(A), headphone safety, neighbor noise documentation

## App
- [Decibel Shield for iOS](https://decibelshield.app/app/): free decibel meter app for iPhone and iPad — real-time dB meter with measurement history, trends, Apple Health sync and background measuring

## Trust & methodology
- [Methodology](https://decibelshield.app/methodology/): how each dataset is produced — the live meter, the sourced decibel chart, the estimated world city map, and the measured US transportation-noise ranking
- [Accuracy & calibration](https://decibelshield.app/accuracy/): why browser meter readings are ±10 dB estimates, how calibration offsets work, and what the meter is and isn't valid for
- [Editorial & data-honesty policy](https://decibelshield.app/editorial-policy/): sourcing standards, corrections, no ads, CC BY 4.0 data licensing

## About
- [Who we are & how we measure](https://decibelshield.app/about/)
- [Press & coverage](https://decibelshield.app/press/): news stories citing this site's noise data (The Post and Courier, Live 5 News, ABC News 4, Datawrapper blog) and the free press kit — all datasets CC BY 4.0
- Identity: decibelshield.app is run by APPSTACK LLC, a small independent app studio; its main product is the Decibel Shield iOS sound level meter (App Store ID 6461600902). This site is a free sound-measurement and open noise-data project: no ads, datasets CC BY 4.0, every published number sourced, corrections shipped within about a week.