IEC 61672 — Class 1 vs Class 2
IEC 61672-1:2013 specifies sound level meter performance in two classes. Class 1 (±1.1 dB at reference) for precision and legal enforcement. Class 2 (±1.4 dB) for general surveys and screening measurements.
IEC 61672-1:2013§5, 5.4, 5.7, Table 2IEC 61672-2:2013IEC 61672-3:2013
Classes
At 1 kHz: Class 1 ±1.1 dB, Class 2 ±1.4 dB. At extremes: ±2.5 / ±3.5 dB. Includes all uncertainty sources.
Weighting Accuracy
A/C/Z per clause 5.4. Class 1: ±1.0 dB from 31.5-8 kHz. Class 2: ±1.5 dB. Against theoretical curve Table 2.
Time Weighting
Clause 5.7: Fast 125 ms, Slow 1000 ms. Class 1: 2% accuracy. Impulse: 35 ms attack, 1500 ms decay in Annex B.
Verification
IEC 61672-2: lab type testing. IEC 61672-3: periodic field verification, typically annual. Less extensive but confirms continued compliance.
Try It Now
Measure SPL with IEC 61672 weighting