IEC 61672-1 Calibration and Verification Requirements
TL;DR
IEC 61672-1 Clause 5.8 requires that sound level meters provide a means of calibration verification using an IEC 60942 sound calibrator (typically 94 dB or 114 dB at 1 kHz). Field calibration must be performed before and after each measurement session. If the pre/post calibration readings differ by more than 0.5 dB (Class 1) or 1.0 dB (Class 2), the measurement session data should be discarded. Laboratory verification against a full set of reference conditions is required periodically per IEC 61672-2.
Field Calibration (Clause 5.8)
Before and after every measurement session, the sound level meter must be verified using a sound calibrator conforming to IEC 60942. Standard calibrators produce either 94.0 dB or 114.0 dB at 1000 Hz. The procedure is straightforward: attach the calibrator to the microphone, read the displayed level, and adjust if necessary.
Acceptance criteria for field checks:
| Class | Maximum drift (pre vs post) |
|---|---|
| Class 1 | 0.5 dB |
| Class 2 | 1.0 dB |
If the drift exceeds these limits, all measurements taken during that session are considered unreliable.
Calibrator Requirements (IEC 60942)
The sound calibrator itself must conform to IEC 60942, which defines two classes: Class 1 (±0.3 dB) and Class 2 (±0.5 dB). A Class 1 sound level meter requires a Class 1 calibrator. The calibrator must be checked annually at an accredited laboratory with traceable reference standards.
Laboratory Verification (IEC 61672-2)
Beyond field calibration, IEC 61672-2 prescribes comprehensive pattern evaluation tests covering the entire operating range. These include frequency response verification at multiple levels, linearity testing, directional response measurements, and environmental sensitivity tests. Laboratory verification typically requires an anechoic chamber, calibrated reference microphone, and traceable signal sources.
Electrical vs Acoustical Calibration
Some instruments support electrical calibration via a known voltage input to the preamplifier, bypassing the microphone. While useful for checking the electronics, electrical calibration cannot verify the microphone sensitivity or frequency response. Full acoustical calibration is always required for compliance.
Multi-Frequency Calibration
For applications requiring accurate measurements across a wide frequency range (e.g., frequency-weighted octave band analysis per IEC 61260-1), single-frequency calibration at 1 kHz may be insufficient. Multi-frequency calibrators producing tones at several octave-band center frequencies provide per-frequency correction factors.
SonaVyx Calibration
SonaVyx provides a 94 dB calibration workflow in the SPL meter. Place your device next to a known calibrator, and SonaVyx calculates the correction offset. Per-frequency correction curves are supported when using a multi-frequency calibrator. This correction is applied to all subsequent measurements until recalibrated. For Class 2 equivalent accuracy, calibration is strongly recommended. See also ANSI S1.4 calibration requirements and Leq/SEL measurement accuracy.
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Last updated: March 19, 2026