Development of a new standard laboratory protocol for estimating the field attenuation of hearing protection devices. Part I. Research of Working Group 11, Accredited Standards Committee S12, Noise

Abstract

This paper describes research conducted by Working Group 11 of Accredited Standards Committee S12, Noise, to develop procedures to estimate the field performance of hearing protection devices ͑HPDs͒. Current standardized test methods overestimate the attenuation achieved by workers in everyday use on the job. The goal was to approximate the amount of attenuation that can be achieved by noise-exposed populations in well-managed real-world hearing conservation programs, while maintaining acceptable interlaboratory measurement variability. S12/WG11 designed two new laboratory-based protocols for measuring real-ear attenuation at threshold, with explicit procedures for subject selection, training, supervision, and HPD fitting. After pilot-testing, S12/WG11 conducted a full-scale study of three types of earplugs and one earmuff tested by four independent laboratories using both protocols. The protocol designated as ''subject-fit'' assessed the attenuation achieved by subjects who were experienced in threshold audiometry, but naive with respect to the use of hearing protection, when they fit HPDs by following manufacturers' instructions without any experimenter assistance. The attenuation results from the subject-fit method corresponded more closely to real-world data than results from the other protocol tested, which allowed the experimenter to coach subjects in HPD use. Comparisons of interlaboratory measurement variability for the subject-fit procedure to previous interlaboratory studies using other protocols indicated that the measurements with the new procedure are at least as reproducible as those obtained with existing standardized methods. Therefore, the subject-fit protocol was selected for consideration for use in

The effects of training format on earplug performance

“…Training is critical for HPD users (Berger, 2000;Royster et al, 1996); however, few studies have been conducted on inexperienced HPD users and individuals from non-occupational populations. Newly hired industrial employees frequently are required to attend safety indoctrination training that lacks recommended hearing loss prevention training components.…”

“…A pair of new earplugs in unopened packages was positioned in front of each participant. The experimenter did not provide assistance or training at the time that the subject was told to insert the hearing protectors (Franks et al, 2000;Royster et al, 1996). Also, no commentary or feedback was available during the fitting, including any suggestions to use the manufacturer's directions placed in front of the subject or on the product packet.…”

Measurement of impulse peak insertion loss for four hearing protection devices in field conditions

“…If one were observing or training a shooter at a firing range, peak impulse levels could easily exceed 140 dB and hearing protection should always be worn. Poorly fit protectors have low REAT attenuations and may provide only a few decibels of protection against high-level impulses (Royster et al, 1996;Murphy & Tubbs, 2007;Murphy et al, 2009). Berger and Hamery (2008) demonstrated that several earplugs provided a small amount of protection.…”

Development of a new standard laboratory protocol for estimating the field attenuation of hearing protection devices. Part III. The validity of using subject-fit data

“…The laboratory-based attenuation values used in the following analyses are the average of each test subjects' two trials in the Subject-Fit 1 test session, and their two trials in the Subject-Fit 2 test session, from the interlaboratory study as reported in Table II of Royster et al ͑1996͒. This provided a single attenuation value for each of 24 subjects at each of four laboratories, based on four attenuation measurements per subject.…”

“…II C and Fig. 1 of Royster et al ͑1996͒. They include the Aearo Company E-A-R ® Classic foam earplug, the PlasMed, Inc. V-51R premolded earplugs ͑5 sizes͒, the Willson Safety Products EP100 premolded earplugs ͑2 sizes͒, and the Bilsom UF-1 earmuffs.…”