Honest label. Phone mics are uncalibrated and compressed — treat this as a
comparison tool, not an instrument. Readings are roughly ±5 dB, and
can be worse at very loud or very quiet levels. Anything below 30 dB reads as <30 — this cannot resolve a truly silent room. Use the offset below to match a real
SPL meter if you have one. Never rely on this for hearing-safety or legal decisions.
CALIBRATION OFFSET+0.0 dB
Saved on this device. Stand beside a known meter and slide until the numbers agree.