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Variability of real-world hearing protector attenuation measurements
Richard Neitzel1, Sebrina Somers, Noah Seixas
1Department of Environmental and Occupational Health Sciences, University of Washington, Seattle, WA 98195-4695, USA. rneitzel@u.washington.edu
The Annals of Occupational Hygiene
|June 20, 2006
Summary
Individual hearing protection varies greatly. This study compared two measurement systems, finding custom earplugs fit better and offered more reliable attenuation than foam earplugs, highlighting the need for personalized assessments.
Area of Science:
- Audiology and Occupational Health
- Personal Protective Equipment (PPE) Performance
Background:
- Field attenuation of hearing protection devices (HPDs) is typically estimated using a derating factor applied to laboratory Noise Reduction Rating (NRR).
- Individual HPD fit significantly impacts actual attenuation, yet variability in measurement systems and over time remains inadequately characterized.
Purpose of the Study:
- To compare attenuation measurements between Real-Ear-at-Threshold (REAT) and Microphone-in-Real-Ear (MIRE) systems.
- To assess the variability of individual attenuation using Personal Attenuation Ratings (PARs) and quantify uncertainty factors (UFs).
- To evaluate worker acceptance of foam versus custom-molded earplugs.
Main Methods:
- Twenty workers were tested using two earplug types (foam and custom-molded) with both REAT and MIRE measurement systems.
- Personal Attenuation Ratings (PARs) were calculated, and variability (between-subject, within-subject, within-day) was assessed.
- Uncertainty Factors (UFs) were determined based on PAR variability.
Main Results:
- Custom-molded earplugs yielded higher mean PARs and greater acceptance compared to foam earplugs across both systems.
- MIRE system showed lower within-day variability than REAT, though MIRE PARs were generally lower than REAT PARs.
- Uncertainty Factors (UFs) ranged from 8.8 to 13.5 dB, influenced by individual measurement variability.
Conclusions:
- Individual-specific attenuation assessment is crucial for hearing protection, moving beyond generalized NRR values.
- Custom-molded earplugs demonstrate superior and more consistent attenuation compared to foam earplugs.
- Understanding and quantifying variability in attenuation measurements is essential for accurate prediction of hearing protection effectiveness.
