Measure RT60 with an Android phone

Yes — a phone can measure RT60 honestly. Stain Acoustics plays a 10-second Farina log sweep through your speakers, records it with the phone (or a USB measurement mic), deconvolves the impulse response, and estimates RT60 with the ISO 3382 T20 method (T30 fallback) — broadband, per octave band, and as a 1/3-octave spectrum from 50 Hz to 10 kHz.

What you need

• An Android phone (Android 9+) and Stain Acoustics.
• Speakers that can play the sweep — wired output (3.5 mm, USB DAC) preferred; the app warns if it detects Bluetooth.
• Optional but better: a USB measurement mic with a .cal file (e.g. Dayton iMM-6C), or run the app's phone-mic calibration wizard once.

The procedure

1. Quiet the room — the app shows the ambient noise floor and flags it if it's high.
2. Open Room Analyser, run AUTO LEVEL so the sweep sits well above the noise floor.
3. Run the sweep from the listening position. Timing metrics (RT60, EDT, C80, D50) come from the uncalibrated impulse response; mic calibration is applied to the frequency response only — so timing numbers are honest even on a bare phone mic.
4. Read the result against your room's purpose (music / cinema / voice), check which octave bands ring longest, and export the impulse response as 24-bit WAV if you want to continue in REW.

What a phone measures well — and what it doesn't

Decay times are ratios in time, so they survive an uncalibrated microphone: RT60, EDT and the per-band decay picture are trustworthy on a phone. Absolute SPL and fine frequency-response detail are where a phone mic needs the calibration wizard or a USB reference. The app says so on every relevant screen — honesty about limits is the feature.