IEC 60942 is the international standard for sound calibrators — devices that deliver a precisely controlled sound pressure level (typically 94 dB or 114 dB at 1 kHz) used to calibrate and field-check sound level meters. It defines three classes (LS, Class 1, Class 2) with progressively tighter tolerances on SPL, frequency, and total harmonic distortion.
IEC 60942 (current edition IEC 60942:2017) is the companion standard to IEC 61672 for sound level meters. Sound calibrators conforming to IEC 60942 are the primary tool for verifying that a sound level meter is functioning correctly before, during, and after field measurements. The coupler-style acoustic calibrator — often called a "pistonphone" for low-frequency variants or simply a "calibrator" for 1 kHz units — is placed over the meter's microphone and produces a defined SPL that the meter should read within tolerance.
The standard defines three classes. Class LS (laboratory standard) has the tightest tolerances — SPL ±0.15 dB, frequency ±0.5%, THD ≤1% — and is used at national metrology institutes and top-tier accredited laboratories. Class 1 (SPL ±0.3 dB, frequency ±1%, THD ≤3%) is the typical field calibrator used by environmental and occupational noise professionals. Class 2 (SPL ±0.5 dB, frequency ±2%, THD ≤3%) is suitable for verifying Class 2 sound level meters in workplace surveys.
IEC 60942 also specifies the environmental conditions for verification, including the reference barometric pressure (101.325 kPa) and the pressure correction formula used to adjust SPL readings for ambient pressure deviation. Periodic verification is typically performed annually and requires a calibrated reference microphone with traceability to a national metrology institute.
Occupational noise technicians rely on Class 1 IEC 60942 calibrators (94 dB or 114 dB at 1 kHz) for pre- and post-measurement field checks. A typical workflow: check the calibrator output against the sound level meter before the survey, perform the dosimetry measurements, and re-check after to document that the meter has not drifted. Environmental noise consultants supporting EIS and litigation use Class LS calibrators maintained under accredited laboratory control to maximize defensibility. Calibration laboratories offering IEC 60942 periodic verification must own or have access to a traceable reference microphone — the microphone calibration chain is usually the dominant contribution to the overall SPL uncertainty, typically 0.08–0.12 dB at 1 kHz for accredited labs.
IEC 60942 is cited directly by IEC 61672-3 for sound level meter field checks and periodic verification. ANSI S1.40 is the parallel US standard with technically equivalent requirements. ISO/IEC 17025 accredited laboratories calibrating acoustic calibrators must include SPL, frequency, THD, short-term stability, and battery condition on the calibration certificate, along with the applied pressure correction per IEC 60942 Annex B and an expanded uncertainty statement (k=2). Common audit findings include missing pressure correction, incomplete THD measurement, and outdated reference microphone calibration.
CalibrationOS provides an IEC 60942 verification template that captures every parameter required by IEC 60942:2017 including SPL at reference frequency, output frequency accuracy, total harmonic distortion, short-term stability, and battery condition. The uncertainty calculator automatically applies the Annex B pressure correction using barometric pressure captured alongside the measurement, and propagates reference-microphone uncertainty, environmental uncertainty, and repeatability into the expanded uncertainty reported on the certificate. The reverse-traceability report identifies every sound level meter calibration and field check performed with the acoustic calibrator under investigation, enabling rapid impact assessment if the calibrator is later found out of tolerance — a key ISO/IEC 17025 Section 7.10 requirement.
IEC 60942 is the international standard for sound calibrators. It specifies SPL, frequency, and distortion tolerances for three classes of calibrator (LS, Class 1, Class 2) and the verification procedures used to confirm ongoing compliance.
Class LS (laboratory standard): SPL ±0.15 dB, frequency ±0.5%, THD ≤1%. Class 1 (field): SPL ±0.3 dB, frequency ±1%, THD ≤3%. Class 2 (field, matched to Class 2 sound level meters): SPL ±0.5 dB, frequency ±2%, THD ≤3%.
For routine field checks, an IEC 60942 Class 1 calibrator is sufficient and standard practice. For the periodic laboratory verification under IEC 61672-3, the laboratory's reference calibrator should be Class LS to keep the uncertainty budget small enough to declare Class 1 conformance on the sound level meter.
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