Measurement method · IEC
IEC 61672: sound level meters (Class 1/2)
IEC 61672 is the international standard that defines how a sound level meter must perform. It specifies the electrical and acoustic characteristics an instrument must meet: frequency weightings (A, C, and Z), time weightings, directional response, linearity, and behavior across the audible range. It also sets out the pattern-evaluation and periodic tests that verify them. It divides instruments into two accuracy grades: Class 1 (precision) meters, with tighter tolerances and a wider frequency range for laboratory-grade and regulatory work, and Class 2 (general purpose) meters for routine surveys.
The standard
What IEC 61672 Is
Published by the International Electrotechnical Commission, IEC 61672 is the benchmark that makes a noise measurement traceable and comparable. Regulations and other standards that set noise limits generally require the measuring instrument to meet a specified class under it.
Who uses it
Who Uses It
Manufacturers build and type-test sound level meters to IEC 61672, and calibration laboratories verify them against it. The people who rely on that grading are acoustic consultants, environmental-health officers, occupational-hygiene professionals, and enforcement bodies who measure environmental noise around roads, railways, industry, and construction, or workplace noise for hearing conservation. When a regulation demands a Class 1 or Class 2 instrument, users choose accordingly: Class 1 where precision or legal defensibility is needed, Class 2 for indicative surveys.
Monitoring
How It Relates to Monitoring
A noise measurement is only as credible as the instrument that makes it, and IEC 61672 defines what "Class 1" and "Class 2" mean so that credibility can be specified and checked. Whether readings can be compared against noise limits depends on the meter meeting the required class and being field-calibrated with an acoustic calibrator before and after use. For fixed environmental monitoring the meter runs continuously, logging levels and statistical indices over hours or days; for occupational surveys it is used alongside a dosimeter. In every case the class rating is what tells a regulator or client that the numbers can be trusted.
Devices
Instruments Built to IEC 61672
Instruments in the sensor catalog that follow this method. Each connects to Environet through a Thiamis gateway.
Instruments built to it
Solutions
Solutions That Rely on IEC 61672
Noise Monitoring
Environmental and occupational sound levels
Questions
IEC 61672 FAQ
What is the difference between a Class 1 and a Class 2 sound level meter?
Class 1 meters have tighter tolerances and a wider usable frequency range, making them suitable for precision, laboratory, and legally defensible measurements, while Class 2 meters are general-purpose instruments for routine and indicative surveys. Many regulations specify which class is acceptable for a given task.
What do the A, C, and Z frequency weightings mean?
A-weighting adjusts the measured sound to approximate the sensitivity of human hearing and is used for most environmental and occupational limits; C-weighting is flatter and used for peak and low-frequency assessment; Z-weighting is unweighted (flat) across the range. IEC 61672 defines all three.
Does an instrument meeting IEC 61672 still need calibration?
Yes. IEC 61672 sets the design and type-test requirements, but each meter must still be periodically laboratory-verified and field-calibrated with an acoustic calibrator immediately before and after measurement. Field calibration confirms the whole measurement chain is accurate on the day.
How do I put together a compliant noise monitoring configuration?
Choose a sound level meter of the class your task or regulation requires (Class 1 for precision and legal work, Class 2 for surveys), with a matching acoustic calibrator, and add a dosimeter for personal exposure. Use the configurator to build a noise monitoring configuration for environmental or occupational use.
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