ISO 4869-1:2018

Overview

ISO 4869-1:2018 - "Acoustics - Hearing protectors - Part 1: Subjective method for the measurement of sound attenuation" defines a laboratory, subjective method to measure the sound attenuation of hearing protectors (earplugs, earmuffs, helmets) at the threshold of hearing. The standard produces reproducible attenuation values under controlled conditions and is intended for use in test laboratories, product development and compliance assessment. It also notes limitations for amplitude‑sensitive devices and low‑frequency masking effects below 500 Hz.

Key topics and technical requirements

• Test signals: Pink noise filtered into one‑third‑octave bands (centre frequencies 125 Hz–8 000 Hz; 63 Hz optional).
• Test site and sound field: Multi‑directional sound incidence with strict sound pressure uniformity - measurements at multiple positions must not deviate more than ±2.5 dB (right‑left difference ≤ 3 dB).
• Reverberation time: Maximum reverberation time in the test space is 1.6 s for each test signal.
• Ambient noise: Maximum permissible ambient noise levels are specified (see Table 2 in the standard) to allow threshold‑level testing down to −10 dB HL.
• Test equipment: Equipment must cover ~112 Hz (or 56 Hz if 63 Hz band used) to 9 000 Hz and generate sound pressure levels from at least 10 dB above the subject’s occluded threshold to 10 dB below the open threshold.
• Microphone and directionality checks: Directional microphone free‑field rejection and allowable field variation are specified to evaluate sound‑field randomness (refer to Table 1).
• Test subjects & procedure: The method is subjective - thresholds are measured with and without protectors; attenuation is the difference in thresholds in dB.
• Limitations: Method can underestimate attenuation for level‑dependent (amplitude‑sensitive) protectors at high SPLs; physiological masking can overestimate attenuation below 500 Hz.

Applications and users

ISO 4869-1 is used by:

• Hearing protector manufacturers for R&D and product performance data
• Acoustic test laboratories performing standardized attenuation measurements
• Occupational health and safety professionals assessing HPD (hearing protection device) performance
• Certification bodies and compliance testers comparing products For more representative field performance, the standard recommends ISO/TS 4869‑5.

Related standards

• ISO/TS 4869‑5 (field performance methods)
• ISO 8253‑2 (sound field audiometry)
• IEC 61260‑1 (one‑third‑octave filter specs)
• ISO 389‑1 (reference equivalent threshold SPLs)

Keywords: ISO 4869-1, hearing protectors, sound attenuation, subjective method, laboratory testing, earplugs, earmuffs, pink noise, one‑third‑octave bands, audiometric threshold.