HowLoudBest Decibel Meter Apps: What Actually Matters
A good decibel meter app does five things: takes raw audio with system processing switched off, applies real A-weighting, reports an energy average (Leq) as well as the live value, lets you calibrate, and keeps a history you can export. Animated needles, "sound recognition" and ten colour themes add nothing to accuracy.
The five features that matter
1. Raw microphone input
Phones apply automatic gain control, noise suppression and echo cancellation to every microphone stream by default, which squashes loud sounds and hides quiet ones. The app must request the unprocessed "measurement" audio mode. If a loud clap barely moves the reading, processing is still on.
2. Real A-weighting
Every noise limit is written in dB(A). Some apps simply subtract a constant instead of filtering; the giveaway is that bass-heavy sounds read the same as voices. Look for "IEC 61672 A-weighting" or the ability to switch between A, C and Z and watch the readings change on a bass-heavy source. See dBA vs dBC.
3. Leq averaging and time weighting
The number regulators use is the Leq, an energy average over the measurement period, not the arithmetic mean of the display. The live value should use the standard Fast (125 ms) or Slow (1 s) time weighting. Min and peak values should be kept for the whole session.
4. Calibration
Every phone microphone has a different sensitivity. A calibration offset, ideally saved per device, is what turns a good app into a usable meter. Some apps come with per-model profiles; a manual offset against a reference meter works as well.
5. History and export
For a noise diary or a workplace check you need saved sessions with date, time, duration, Leq, peak and ideally a location, exportable as a PDF or CSV.
Features that are nice but secondary
- A level-over-time chart (very useful for spotting events)
- Dosimeter mode that accumulates daily exposure against the 85 dB limit
- Frequency spectrum display
- Support for an external calibrated microphone
- Watch or widget for quick checks
Features that are mostly marketing
- Analogue-needle skins and "vintage meter" looks
- "Laboratory accuracy" claims without a stated calibration method
- Sound identification ("this is a dog") in place of measurement functions
- Ads that interrupt a running measurement
How HowLoud compares
HowLoud was built around exactly the five points above: raw audio, IEC 61672-1 A-weighting implemented as a digital filter, Leq plus min and peak with Fast time weighting, a per-device calibration offset, and a session history with map location and PDF export. Live measurement, history and charts are free; PDF export is a one-time purchase. There are no ads and no account. The same engine runs in the free online meter if you want to try it before installing anything.
Testing an app in five minutes
- In a quiet room, the reading should settle around 30–40 dB, not 0 or 20.
- Talk at normal volume at arm's length: 60–65 dB.
- Clap once hard: the peak should jump to 90+ dB and the live value should fall back within a second.
- Play music with bass and switch A/C weighting: the C reading should be higher.
- Check that a saved session shows Leq, peak and duration.
Frequently asked questions
Are free decibel meter apps accurate?
Some are, if they use raw audio and real weighting. Price is not a predictor; the five checks above are.
Do I need an app, or is a website enough?
For a quick reading a web meter is enough. For a noise diary, background measurement or exports, an app is more practical.
Can an app replace a professional sound level meter?
For everyday and preliminary measurements, yes. For legal or compliance work, no; see meter classes and accuracy.