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07Accuracy

Calibration

Trim the level against a 94 dB reference, or load your measurement mic's own calibration file.

ProVerified for version 1.0.2 · Updated October 17, 2026

Calibration lives in Settings → Device and is part of Pro. There are three layers, and they stack:

  1. Device compensation. On models SoundMess Lab has a curve for, Pro applies it automatically and the device pill turns to Calibrated. Those are the iPhone 12, 13, 14 and 15 families, iPhone SE (2nd and 3rd generation), iPad Air (4th generation, Wi‑Fi) and the Wi‑Fi 11-inch and 12.9-inch M2 iPad Pro. Other models, cellular iPads included, stay in Baseline.
  2. Reference-tone trim. Shifts every SPL reading so it matches a known 94 dB source.
  3. External mic file. Applies the calibration curve that came with a measurement microphone.

Trim against a reference tone

  1. Open Settings → Device → Reference-tone calibration. You need a 94 dB SPL, 1 kHz source: a handheld acoustic calibrator, or a known-good calibrated speaker playing a 1 kHz tone at 94 dB. Tap I have a 94 dB reference.

  2. Position the phone. Hold the primary microphone (the bottom edge on iPhone, the top edge on iPad) 2–3 cm from the source, in a quiet room. Tap I'm in position.

  3. Hold steady while SoundMess Lab averages the level over 3 seconds.

  4. Check the trim. It shows Measured, Reference (94.0 dB SPL) and the Trim between them. Tap Apply trim, or Retry.

SoundMess Lab's Reference Tone sheet: Before you start, asking for a 94 dB SPL 1 kHz reference source, with an I have a 94 dB reference button.
The first step of the reference-tone wizard.

The trim then applies to every future SPL reading. Settings shows it next to Reference-tone calibration (for example +3.2 dB), and Clear calibration trim removes it.

An external measurement mic

A measurement microphone usually comes with a calibration file for that exact capsule. Connect the mic, then in Settings → Device tap Import external mic cal file and choose the file in Files.

  • Formats: .txt or .frd, one point per line as frequency and dB (a third phase column is ignored), separated by spaces, tabs or commas.
  • Comments: lines starting with *, #, ; or // are skipped, as is a header before the first data line.

Once imported, Settings shows the file's name under External mic, the device pill shows that name with Calibrated, and Clear external calibration removes it. Check Measurement info to confirm the external mic is the active input.

Related

Still stuck? Write to zhi@nonoaudio.com. Support page