IEC 61672-1 Periodic Testing and Verification per IEC 61672-2
TL;DR
IEC 61672-2:2013 specifies pattern evaluation tests and periodic verification procedures for sound level meters. Periodic verification should be performed at intervals not exceeding 2 years (many jurisdictions require annual verification). Tests include frequency weighting response, level linearity, time weighting behavior, peak response, and self-generated noise. Testing must be performed by an accredited laboratory with reference equipment traceable to national standards. Records must be maintained showing pass/fail status for each test.
Purpose of Periodic Testing
Sound level meters can drift over time due to microphone aging, electronic component degradation, physical damage, or environmental exposure. IEC 61672-2 defines the procedures to verify that an instrument continues to meet its original class specifications. This is separate from field calibration with a sound calibrator — periodic testing is a comprehensive laboratory evaluation.
Test Interval
IEC 61672-2 does not mandate a specific interval but recommends periodic verification at intervals appropriate to the instrument's use and environment. In practice:
- Most national metrology organizations recommend annual verification
- Some jurisdictions mandate verification every 2 years
- Instruments used in harsh environments (outdoor, industrial) may need more frequent checks
- Instruments used only occasionally may follow a 2-year cycle
Required Tests (IEC 61672-2)
The periodic verification includes the following assessments:
- Frequency weighting — verify A, C, Z response at specified frequencies against tolerance limits
- Level linearity — verify the level indication from the lower to upper limit of the linear operating range at 1 kHz
- Time weighting — verify Fast, Slow, Impulse detector response using tone bursts
- Peak response — verify LCpeak detector with prescribed signal
- Self-generated noise — measure the instrument's noise floor
- Overload indication — verify overload detector triggers within tolerance
Accreditation Requirements
Testing laboratories should be accredited to ISO/IEC 17025 for the relevant test methods. The reference equipment used for verification must have calibration traceable to national measurement standards. Results are documented in a verification certificate listing each test, the measured values, the acceptance limits, and the pass/fail determination.
Consequences of Failure
If an instrument fails periodic verification, measurements taken since the last passing verification may be called into question. For legal or regulatory measurements (environmental noise enforcement, occupational health compliance per OSHA), an expired or failed verification certificate can invalidate measurement data in court.
Digital Instruments and SonaVyx
Software-based measurement systems like SonaVyx implement the signal processing algorithms with mathematical precision — the DSP code does not drift. However, the input transducer (phone microphone or audio interface) remains an analog component subject to the same degradation risks. Regular calibration checks with a sound calibrator help verify the complete signal chain. For standards comparison, see ANSI S1.4 and the broader IEC 61672-1 hub page.
Try It Now
Open this measurement tool in your browser — free, no download required.
Last updated: March 19, 2026