ISO/TS 4869-5:2006

Overview

ISO/TS 4869-5:2006 - "Acoustics - Hearing protectors - Part 5" specifies a laboratory method for estimating the noise reduction of passive hearing protectors by measuring hearing thresholds with fitting by inexperienced test subjects. The core principle is simple: measure the open-ear threshold (no protector) and the occluded-ear threshold (with protector); the difference is the individual noise reduction. Measurements are made twice per subject at sound pressure levels close to the threshold of hearing; results are intended to represent the performance typical users achieve in real-world occupational settings.

Key Topics and Requirements

• Purpose: Provide realistic estimates of hearing protector performance when worn by untrained or unmotivated users (ear-plugs, ear-muffs).
• Measurement principle: Threshold-based test - difference between occluded and open-ear thresholds.
• Repeatability: Each measurement is performed twice on each subject to reduce variability.
• Representative levels: Tests are done at low sound pressure levels (near threshold) but are considered representative for higher levels; not applicable to level-dependent protectors above their effective activation point.
• Test site and environment: Requirements for test room acoustics (reverberation time), background noise control and general validity conditions.
• Test equipment: Audiometric and acoustic equipment conforming to referenced IEC standards (e.g., IEC 60645-1, IEC 61672-1, IEC 61260).
• Test subjects: Criteria for subject acceptance/dismissal (age, hearing thresholds, anatomical considerations, prior experience), number of subjects required, otoscopic inspection, limits on spectacles/jewellery, and maximum tests per subject.
• Product handling: Rules for product samples including custom-moulded earplugs, instructions to subjects, and variable headband or band-force considerations.
• Data processing: Calculation of individual and group noise reduction values and assessment of measurement uncertainty (informative Annex A).
• Reporting: Standardized reporting of results and associated uncertainty.

Applications and Users

Who uses ISO/TS 4869-5:

• Manufacturers evaluating real-world performance of ear-plugs and ear-muffs.
• Test laboratories performing independent attenuation assessments.
• Occupational hygienists and safety officers selecting and specifying hearing protection for workplaces.
• Regulators and procurement teams needing representative attenuation data for policy, labeling, and purchasing decisions.

Practical uses:

• Estimating the noise reduction achievable by typical, inexperienced users.
• Comparing product designs under realistic fitting conditions.
• Informing training and fit-check programs by highlighting real-world attenuation gaps.

Related Standards

• ISO/TS 4869 series (Parts 1–6): Part 1 (subjective attenuation), Part 2 (effective A-weighted levels), Part 3 (insertion loss), Part 4 (level-dependent), Part 6 (active NR - under development).
• Normative references cited: IEC 60263, IEC 60645-1, IEC 61260, IEC 61672-1, and the GUM guide for uncertainty.