Why Phone Decibel Meter Apps Show Different Numbers
It is common for two decibel apps on the same phone to disagree by 5 to 15 dB. Neither is necessarily broken. The difference comes from the reference level each app assumes and from how your phone's microphone and audio processing behave.
Main reasons
- Reference level: a phone reports a digital signal, not pressure. Each app picks an offset to turn it into dB SPL.
- Microphone and processing: phones filter wind and low frequencies and some apply automatic gain, which lowers loud peaks and thumps.
- Weighting: dB(A) de-emphasizes low frequencies, like human hearing. Footstep thuds are low-frequency, so they can read lower than they feel.
- Averaging: fast, slow, peak or Leq readings of the same sound give different numbers.
How to calibrate
- Borrow or compare with a sound level meter, or a reading you trust, in a steady sound such as a fan.
- Set the app's calibration offset so both match.
- Keep using the same phone in the same spot. Consistency matters more than the absolute number.
Even calibrated, a phone is not a certified meter. It is best at showing when and how often noise changes compared with your normal background.
Consistent logs
Hushlog measures dB(A), lets you set a calibration offset, and records Lmax, Leq, L10 and L90 for each event so you can compare nights on the same scale.
Hushlog — coming soon to Google Play