Measurement microphone specifications can be confusing, and the gap between marketing copy and technical reality is sometimes wide. This article explains what the key specifications actually mean for real-world measurement performance, how to read IEC 61094 compliance claims correctly, and how to match microphone performance to your application without paying for specifications you will never need.
The most important distinction in measurement microphone selection is not between brands — it is between microphone types and calibration documentation classes. Free-field, pressure-field, and random-incidence microphones are physically similar but designed for different acoustic field conditions. Using the wrong type in a given measurement introduces a systematic error that calibration cannot correct.
IEC 61094 Class 1 and Class 2 describe the specification tolerance limits of the microphone — Class 1 is tighter. But the calibration certificate type matters more for measurement uncertainty: a QA/AC factory certificate confirms specification compliance but does not state the specific measured sensitivity with uncertainty. An ISO/IEC 17025 accredited calibration certificate states the measured open-circuit sensitivity at each calibration frequency with an expanded measurement uncertainty. For most compliance measurement programmes, the accredited certificate is the appropriate choice regardless of microphone class.
A well-matched measurement microphone selection — correct field type, appropriate class, and ISO/IEC 17025 accredited calibration — delivers defensible, traceable results at a cost that reflects what the application genuinely requires. The goal is not to buy the best microphone available; it is to buy the right microphone for the measurement, with documentation that will stand scrutiny at the time of the measurement and years later when results are reviewed.