Overview
EN 61094-8:2012 (CLC adoption of IEC 61094-8:2012) defines methods for determining the free-field sensitivity of working standard microphones by comparison. It is applicable to working standard microphones that meet IEC 61094-4 and describes comparative calibration techniques using a laboratory or working standard microphone calibrated to relevant parts of the IEC 61094 series. The standard covers measurements performed in acoustical environments that approximate an ideal free-field (for example, a high‑quality free‑field chamber) and methods that use post‑processing or time‑selective techniques to minimise the effects of imperfect test spaces.
Key topics and technical requirements
- Scope and applicability: Procedures specifically for working standard microphones and applicable also to laboratory standards where relevant.
- Reference microphones and traceability: Use of laboratory or working standard microphones calibrated according to IEC 61094 parts (IEC 61094‑3, ‑2, ‑5, ‑6 or this part).
- Test environments: Methods for establishing free‑field conditions, including acoustic absorption, hemi‑anechoic/free‑field chambers and post‑processing to simulate free‑field behavior.
- Excitation methods: Sequential and simultaneous excitation strategies, and use of monitor microphones and calibrated sound sources.
- Time‑selective techniques: Methods to isolate direct sound from reflections when ideal free‑field conditions are not available.
- Factors affecting free‑field sensitivity: Polarizing voltage, acoustic centre, angle of incidence, mounting configuration and environmental dependence.
- Uncertainty and validation: Guidance on uncertainty components (reference sensitivity, microphone output measurement, sound pressure differences between reference and test microphones, indirect sound, signal processing, microphone capacitance, system non‑linearity) and validation/verification of the calibration system.
- Informative annexes: Practical substitution calibration examples and time‑selection implementations.
Applications and who uses it
EN 61094-8:2012 is used by:
- Calibration laboratories and national metrology institutes for calibrating working standard microphones.
- Acoustic test laboratories performing free‑field acoustic measurements.
- Microphone and preamplifier manufacturers for production verification and traceable sensitivity determination.
- Environmental and aerospace acoustics specialists and consultants who require traceable microphone calibrations for field or chamber measurements.
Practical uses include establishing traceable free‑field sensitivity for microphones used in sound level meters, acoustic research, product testing, and noise monitoring systems.
Related standards
- IEC/EN 61094‑1 - laboratory standard microphone specifications
- IEC/EN 61094‑2 - primary reciprocity method (pressure)
- IEC/EN 61094‑3 - primary reciprocity method (free‑field)
- IEC/EN 61094‑4 - specifications for working standard microphones
- IEC/EN 61094‑5, ‑6, ‑7 - complementary calibration and actuator methods
- ISO 26101 - qualification of free‑field environments
Keywords: EN 61094-8:2012, measurement microphones, free-field calibration, working standard microphones, calibration by comparison, free-field chamber, time-selective techniques, microphone sensitivity, calibration uncertainty.