SPL Reference Calibration
Set absolute dB SPL reference using a 94 dB calibrator
Required For
- • Legal SPL limit compliance
- • Safety/noise ordinance documentation
- • Professional acoustic reports
Equipment Needed
- • SPL calibrator (94 dB @ 1kHz)
- • Measurement microphone
Skip if only doing EQ/tuning work
Calibration Procedure
Open SPL tab, select Z-weighting
Flat frequency response for calibration (Z = no weighting)
Apply calibrator to microphone capsule
Ensure tight seal, centered positioning, and calibrator is stable
Note current SPL meter reading
Adjust calibration offset until meter reads 94.0 dB
In right sidebar "Calibration" section - adjust until display matches calibrator output
Verify repeatability
Remove and reapply calibrator - should read 94.0 ±0.5 dB consistently
Understanding the “Required Offset” value
After calibration, AudioMap shows a Required Offset value. Here’s what it means and how to read it as a diagnostic.
What it is
A scaling constant that maps digital level (dBFS) to acoustic level (dB SPL) for your specific mic + preamp gain.
It is not a sound level — it represents what 0 dBFS (digital full-scale clipping) would correspond to in dB SPL on your current chain.
What it should be
- • 115–130 dB — healthy gain structure
- • Up to ~140 dB — acceptable with deliberately low preamp gain
- • Outside that range — see diagnostics below
The exact number depends on mic sensitivity and preamp gain. Two correctly calibrated rigs can land on different offsets.
If your offset is…
115–130 dB — healthy
Gain structure is in the right place. You have headroom for loud sources and enough signal to keep the noise floor low. Carry on.
Above ~150 dB — preamp gain too low
The mic signal is arriving at the ADC very quietly, so the offset has to be large to translate tiny digital values into real SPL. Real measurements will be noisy and may not resolve quiet detail.
Below ~110 dB — preamp gain too high (or wrong reference)
Either the preamp is amplifying the signal too much (risk of digital clipping during real-world loud sources), or the wrong calibration reference SPL was entered during calibration.
Important
- • Required Offset is a scaling number, not a sound level — a large offset value does not mean the room is at that SPL.
- • Recalibrate any time you change mic, preamp, interface, or gain settings.
- • Replace calibrator batteries regularly — low voltage affects accuracy.
- • Recalibrate if temperature changes significantly.
- • Most calibrators need annual certification.
- • Different microphones legitimately produce different offsets — don’t expect yours to match someone else’s.