HowLoudHowLoud: The Decibel Meter App for iPhone and Android
A sound level meter that behaves like an instrument, not a toy: raw microphone input, real A-weighting, Leq averaging, calibration, and a history you can turn into a PDF noise report.
Free to measure and save sessions. PDF export is a one-time purchase. No ads, no sign-up, works offline.
What the app does
- Live dB(A) reading with the same fluid display as this site: the colour follows the zone, green under 60 dB, orange to 84 dB, red from 85 dB.
- Min, average (Leq) and peak for every session, using Fast time weighting and an IEC 61672-1 A-weighting filter.
- Session history with date, duration, statistics, a level chart and the location where you measured; seven days free, 90 days with the one-time purchase.
- Compare screen that places your reading on a scale of familiar sounds, from a whisper to a jet.
- PDF noise report: an A4 document with the stats, time-series chart, mini-map and a disclaimer, ready to attach to a complaint or share with a landlord.
- Calibration offset to match a reference meter, saved on the device.
- Private by design: no account, no analytics, no audio recording. Everything stays on the phone.
Who it is for
Documenting noise
Neighbours, building work, traffic, a bar downstairs. Measure, save, export, done. Read the neighbour noise guide.
Protecting your hearing
Check the gym, the commute and the workshop against the 85 dB rule. See safe decibel levels.
Comparing products
Fans, fridges, dishwashers, air purifiers, cars: put two side by side and read the Leq.
Classrooms and offices
Use the phone as a portable meter, or put the classroom noise meter on the board.
App or website?
The online decibel meter uses the same engine and is the fastest way to take a reading. The app adds saved history, background operation, the compare scale and PDF export, and it is a better microphone setup because iOS and Android give apps the unprocessed measurement audio mode more reliably than a browser tab.
Frequently asked questions
Is the HowLoud app free?
Yes. Measuring, statistics, charts and a seven-day history are free with no ads. A single one-time purchase unlocks PDF export and a 90-day history.
How accurate is it?
Within about ±3 dB on iPhones and most recent Android phones for levels between 40 and 95 dB(A), after calibration. It is an estimate, not a certified instrument; see phone accuracy.
Does it record audio?
No. The app computes a level from the microphone signal many times a second and discards the audio immediately. Sessions store numbers only.
Does it work offline?
Yes, fully. The only network use is the map tile on the session detail screen if you saved a location.