Overview
EN ISO 11904-1:2002 - "Acoustics - Determination of sound immission from sound sources placed close to the ear - Part 1: Technique using a microphone in a real ear (MIRE technique)" specifies a validated method for measuring sound exposure from sources located very close to the ear. The standard defines how to use miniature or probe (ear canal) microphones inserted in human subjects to measure ear-canal sound pressure, and how to convert these measurements into free‑field or diffuse‑field related equivalent continuous A‑weighted sound pressure levels (L Aeq). Applicable frequency range: 20 Hz to 16 000 Hz.
Key topics and requirements
- Measurement principle: Use of the microphone‑in‑real‑ear (MIRE) technique - probe microphones placed at defined positions in human ear canals to capture actual ear exposure.
- Instrumentation: Requirements and guidance for ear canal microphones, reference field microphones, calibration checks and appropriate filters.
- Subjects and positioning: Selection and handling of human subjects, specified ear‑canal microphone positions and mounting practices to ensure consistent results and safety.
- Conversion and reporting: Procedures to convert measured ear‑canal SPLs to free‑field or diffuse‑field related levels, including A‑weighting and summation rules for equivalent continuous sound pressure levels.
- Frequency response: Guidance for determining free‑field and diffuse‑field frequency responses for selected ear canal positions and for establishing reference sound fields (free, quasi‑free, diffuse).
- Uncertainty and quality control: Annexes provide examples of measurement uncertainty and uncertainty analysis; the standard also requires documenting calibration, measurement arrangement checks and a comprehensive test report.
Practical applications and users
EN ISO 11904-1 is used when a conventional ambient measurement does not represent the ear’s exposure because the source is very close to the ear. Typical applications include:
- Testing and certification of headphones, earphones and in‑ear devices (consumer audio, professional monitors).
- Evaluation of hearing protectors with integrated audio or communication facilities.
- Workplace noise assessments where close‑to‑ear exposure occurs (nail guns, head‑mounted tools, communication headsets).
- Occupational hygienists, acoustic engineers, product test laboratories, hearing conservation specialists, manufacturers of audio/headset equipment, and regulatory/test authorities.
Related standards
- ISO 11904-2 - Manikin technique (alternative method using an acoustic manikin).
- ISO 8253-2 - Sound field audiometry (referenced normative publication).
Keywords: EN ISO 11904-1, MIRE technique, microphone in real ear, ear canal microphone, sound immission, free-field related level, diffuse-field, A-weighted L Aeq, headphone testing, occupational noise.
