Overview
ISO 4869-6:2019 - "Acoustics - Hearing protectors - Part 6" specifies standardized test methods for determining the sound attenuation of active noise reduction (ANR) earmuffs. The standard defines how to measure the active insertion loss (AIL) provided by the ANR circuit and how to combine that with passive attenuation to derive the total attenuation in octave bands. It applies to steady (non-impulsive) noise exposures and accounts for the acoustical interaction between wearer and device using both REAT and MIRE measurement techniques.
Key topics and technical requirements
- Scope and limitations
- Focused on ANR (active noise reduction) earmuffs; not intended for impulsive noises.
- Test specimens and conditioning
- Four pairs of earmuffs required; power source fully operational. Conditioning at (22 ± 5) °C, relative humidity ≤ 85 %.
- Measurement techniques
- Passive attenuation measured by REAT (ISO 4869-1).
- Active attenuation measured by MIRE (microphone-in-real-ear) per ISO 11904-1 with closed earcanals.
- Test signals and levels
- Broadband noise (pink noise suitable) from 50 Hz (or 100 Hz) to 10 000 Hz for active insertion loss measurement.
- A-weighted levels for AIL measurement usually between 85 dB and 95 dB (up to 110 dB if device has a threshold).
- Red noise used to verify linear operation in low frequencies; level checks up to 110 dB.
- Protocol and statistical sampling
- Sixteen test subjects (both ears measured), each specimen tested by four subjects.
- Procedures for handling oscillation or malfunction and for reporting such events.
- Calculation
- Active insertion loss = difference between passive and active MIRE/REAT spectra per subject.
- Total attenuation computed per subject by combining passive REAT and measured AIL (detailed computation in the standard).
Practical applications
- Validating and certifying ANR earmuff performance for manufacturers and test laboratories.
- Supporting product development and R&D for hearing protectors targeting low-frequency noise control.
- Supplying objective data for safety officers, procurement teams, and hearing conservation programs when selecting ANR devices for industrial environments.
- Establishing evidence for marketing claims and regulatory compliance regarding attenuation values.
Who uses this standard
- Hearing protector manufacturers and design engineers
- Accredited acoustic test laboratories
- Occupational hygienists, safety managers, and procurement specialists
- Regulatory bodies and conformity assessment organizations
Related standards
- ISO 4869-1 - Subjective REAT method for passive attenuation
- ISO 4869-2 - Estimation of effective A-weighted sound levels with protectors
- ISO 11904-1 - MIRE technique (microphone in real ear)
- IEC 61094-4 - Working standard microphone specifications
Keywords: ISO 4869-6:2019, active noise reduction earmuffs, ANR earmuffs, active insertion loss, MIRE, REAT, sound attenuation, hearing protectors, acoustics standard.