Evaluating Earplug Performance over a 2-Hour Work Period with a Fit-Test System

Abstract

Workers rely on hearing protection devices to prevent occupational noise-induced hearing loss. This study aimed to evaluate changes in attenuation over time for properly fit devices when worn by workers exposed to hazardous noise. Earplug fit testing was accomplished on 30 workers at a brewery facility with three types of foam and three types of premolded earplugs. The personal attenuation ratings (PARs) were measured before and after a 2-hour work period while exposed to hazardous noise levels. The minimum acceptable initial PAR was 15 dB. Average decreases in PAR ranged from -0.7 to -2.6 dB across all six earplug types. Significant changes in PAR were observed for the Foam-1 ( p = 0.009) and Premold-3 ( p = 0.004) earplugs. A linear mixed regression model using HPD type and study year as fixed effects and subject as random effect was not significant for either fixed effect ( α = 0.05). Ninety-five percent of the final PAR measurements maintained the target attenuation of 15 dB. Properly fitting earplugs can be effective at reducing worker's noise exposures over time. The potential for a decrease in attenuation during the work shift should be considered when training workers and establishing the adequacy of protection from hazardous noise exposures.

Keywords: duration; fit testing; hearing protection; noise exposure; occupational hearing loss; personal attenuation rating.

Figure 1

Earplug type, make, model, material, noise reduction rating, and sizing. (Image credit: William Murphy.)

Figure 2

Initial and final personal attenuation rating (PAR) outcomes (dB) for individual subjects meeting the minimum 15 dB PAR for each earplug before the 2-hour work-shift. Circles were used for the earplugs evaluated in the first year, squares for the second year, and diamonds for the third year. A color code for symbols (orange, blue, purple, green, yellow, orange) are matched in Figs. 2 and 3 . Colors for lines are for clear visualization only.

Figure 3

Change in personal attenuation rating (dB) for each subject and hearing protector worn for a 2-hour work period. Open symbols represent subjects who had inconsistent responses and were not included in the analysis. Circles were used for the earplugs evaluated in the first year, squares for the second year, and diamonds for the third year.

Figure 4

Box plots for medians and percentiles of initial personal attenuation ratings (PARs), final PARs, and the difference between final and initial attenuation measurements by earplug type. The median (–), 25th and 75th quartiles are depicted with the box. The vertical lines extend from the ends of the box to the 5th and 95th percentile values. A circle (∘) represents outlier that is more than the upper quartile plus 1.5 × interquartile range or less than the lower quartile minus 1.5 × interquartile range.