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NIOSH Hearing Loss Research Program Review NIOSH Publications on Noise and Hearing The National Academies - Advisors to the Nation on Science, Engineering, and Medicine

What does the HLR Program Do?

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Research Goal 1

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Research Goal 4

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R&D Portfolio - Research Goal 2.1:
Develop measurement and rating methods that are representative of real-world performance of hearing protection devices

Using the EPA’s 1981 estimates of noise exposed workers and current DOL statistics of U.S. production workers, approximately 13.5 million workers in the U.S. wear or should wear HPDs.[23], [24] Every HPD has a NRR to guide employers and workers as to which HPDs are sufficiently protective for different workplace conditions. However, the current EPA regulation for NRRs results in overestimates of the protection achieved in the workplace by most users.1 The regulation specifies the ANSI S3.19-1974 experimenter-fit protocol as the only acceptable acoustic test standard for hearing protection devices.[25] The overestimation of protection may result in workers being overexposed to noise.

HLR program scientists verified the overestimates of experimenter-fit NRRs in tests of HPDs in occupational settings. They demonstrated that the experimenter’s fitting instructions bias measurements of attenuation. The experimenter strives to achieve the highest possible NRR and repeatable results in the lab through excellent HPD fit. However, most workers who wear HPDs lack similar motivation and training. Unlike the experimenters, they are often unaware that compromised HPD fit reduces its attenuation.

HLR program scientists based efforts to revise the existing EPA regulation on research that test protocols and rating methods, partnerships with government agencies and manufacturers, and active participation with standards setting bodies. In 1988, the EPA sought technical assistance from NIOSH with a regulatory audit for labeling of a particular HPD. The audit resulted in a relabeling of the HPD and initiated a broad research effort to develop testing methods that were more representative of workers’ use. Between 1990 and 1994, the HLR program executed two inter-laboratory studies that included six testing laboratories from government, industry, and academia. The studies demonstrated that a subject-fit protocol reduced inter-laboratory variability compared to inter-laboratory variability using other fit methods, including the experimenter-fit protocol.[26], 3,  [27], [28]  In 1997, NIOSH established an inter-agency agreement with EPA. The initial work phase was to develop testing and rating methods for passive and electronically augmented hearing protectors. Since 2002, the HLR program has provided the EPA technical assistance with the goal of issuing a revised regulation on HPD labeling.

National and international collaboration efforts of the HLR program have influenced hearing protector testing practices, performance ratings, testing standards, and regulations worldwide. Our scientists participated in the NCHA Task-force on hearing protection testing 1995[29] which first recommended the use of a subject-fit protocol following the completion of the inter-laboratory studies. Since 1990, our scientists have been an active member of ANSI S12 working groups for standards development related to hearing protector testing and rating. In 2003 and again in 2005, HLR program staff members were appointed as U.S. delegates to ISO technical committee meetings for international standards development of hearing protection testing and rating.

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[23] EPA [1981]. Noise in America: the extent of the noise problem. Washington DC: U.S. Environmental Protection Agency, EPA Report No. 550/9-81-101.

[24] US Department of Labor [2005] Comparison of Production Workers, Not Seasonally Adjusted, before and after the March 2004 Benchmark. accessed Sept. 7, 2005.

[25] ANSI S3.19-1974 [1974]. American National Standard Method for the Measurement of Real-ear Protection of Hearing Protectors and Physical Attenuation of Earmuffs. New York: American National Standards Institute.

[26] Royster JD, Berger EH, Merry CJ, Nixon CW, Franks JR, Behar A, Casali JG, Dixon-Ernst C, Kieper RW, Mozo BT, Ohlin D, Royster LH [1996]. 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. J Acoust Soc Am 99, 1506–1526.

[27]Murphy WJ, Franks JR, Krieg EF [2002]. Hearing protector attenuation: Models of attenuation distributions. J Acoust Soc Am 111 (5) Part 1: 2109-2116.

[28] Murphy WJ, Franks JR, Berger EH, Behar A, Casali JG, Dixon Ernst C, Krieg EF, Mozo BT, Ohlin DH, Royster JD, Royster LH, Simon SD, Stephenson C [2004]. Development of a new standard laboratory protocol for estimation of the field attenuation of hearing protection devices: Sample size necessary to provide acceptable reproducibility. J Acoust Soc Am 115 (1): 311-323.

[29] Royster LH [1995]. In Search of a Meaningful measure of Hearing protector Effectiveness, Spectrum 12(20 1,6-13.


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