CDC logoSafer Healthier People  CDC HomeCDC SearchCDC Health Topics A-Z
NIOSH - National Institute for Occupational Safety and Health
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 has the program achieved?

In this section ....

Research Goal 1

Research Goal 2

Research Goal 3

Research Goal 4

HLR Databases

Acronym Finder

Outputs and Transfer - Research Goal 2.1:
Develop measurement and rating methods that are representative of real-world performance of hearing protection devices

The results of the inter-laboratory studies are the most important outputs for the efforts in HPD testing and labeling regulations. These studies resulted in four peer-reviewed publications. The first of these papers reported that the subject-fit protocol had the smallest interlaboratory variability. The other papers compared the real-world performance with the subject-fit protocols, examined models for describing HPD attenuation data, and established statistical methods for the analysis of subject sample size to achieve adequate reliability.

In addition to these papers, HLR program scientists wrote papers for conference proceedings, presented them, and sponsored conferences and workshops on hearing protectors. The HLR program organized and provided technical support for the EPA’s 2003 workshop on hearing protector labeling regulation. This conference brought together representatives from nine HPD manufacturers (3M, Aearo, Bilsom, Bose, Gentex, HLI, Moldex Metric, North, Tasco), DOD (Army, Air Force, and Navy), and DOL, OSHA and MSHA.

Intermediate Outcomes

Following the 2003 conference, the EPA opened a docket on revising their hearing protector labeling regulation.[30]

The HLR program research provided the basis for revisions of national and international testing standards which in turn have affected international regulations for rating and certifying hearing protector performance. As the result of a discovery of a bias inherent in the experimenter-fit protocol, OSHA required a 50 percent reduction of the NRR for a HPD when estimating the protected exposure level for workers. MSHA went further, making no allowance for the attenuation of HPDs for mine workers.[31] NIOSH recommended a variable reduction of the NRR that allows for the type of protector: 25 percent reduction for earmuffs, 50 percent for foam earplugs, and 30 percent for all other types of protection.













The ANSI S12.6-1997 standard has been the basis for revisions of several international standards for hearing protector testing and regulations.

>> View What's Ahead for this Research Subgoal


Journal Articles

Franks J, Graydon PS, Chen J, Murphy WJ [2003]. Hearing protector device compendium.

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

Franks JR, Murphy WJ, Johnson JL, Harris DA [2000]. Four earplugs in search of a rating system. Ear & Hearing 21: 218-226.

Franks JR, Themann CL, Sherris C [1995]. The NIOSH Compendium of Hearing Protection Devices. U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, DHHS (NIOSH) Publication No. 95-105.



Murphy WJ [2005]. Derivation of an analytic expression for the error associated with the Noise Reduction Rating. Meeting of Acoustical Society of America Vancouver BC, May 2005.

Murphy WJ [2005]. Current Research Issues for Hearing Protectors. Allied Construction Safety Days Conference, Loveland OH,  March 8, 2005

Murphy WJ, Shaw PB [2005]. Calculation of the Intrinsic Error in Hearing Protector Ratings. National Hearing Conservation Association, Seattle WA, Feb 21 2005.

Murphy WJ, Franks JR, Shaw PB [2004]. Estimating the Precision in Hearing Protectors Ratings Acoustical Society of America / New York, NY. May 2004.

Murphy WJ, Franks JR, [2002]. Current status of standards for testing electroacoustic hearing protectors,” J. Acoust. Soc. Am., Vol. 112 No. 5 Pt. 2, 2317.

Murphy WJ, Franks JR [2001]. A reevaluation of the Noise Reduction Rating. Commissioned Officers Association of the US Public Health, Service, Washington DC, May 29, 2001.

Franks JR, Murphy WJ [2000]. Now what do we do with these good numbers? J Acoust Soc Am Vol. 108 No. 5 Pt. 2, 2620.

Murphy WJ, Franks JR [1999]. Progress on a rating system for hearing protector attenuation. J Acoust Soc Am Vol. 106 No. 4, Pt. 2, 2262.

Murphy WJ, Franks JR [1999]. Reducing hearing protector test time with a minimum audible pressure to field transfer function. J Acoust Soc Am Vol. 106, No. 4, Pt. 2, 2238.

Murphy, WJ, Franks, JR, Harris, DA, Johnson, JL [1999]. Four protectors in search of a rating system, J. Acoust. Soc. Am., 105, No. 2, Pt. 2,1132.

Murphy WJ, Franks JR [1999]. A Rating System in Search of Protectors. J Acoust Soc Am Vol. 105 No. 2, Pt. 2,1131.

Murphy WJ, Franks JR [1998]. Analysis of repeatability and reproducibility of hearing protector real-ear-attenuation-at-threshold measured with three fitting methods. Military Audiology Short Course, February 23-26, Albuquerque, NM.

Murphy WJ, Franks JR. [1998]. Analysis of repeatability and reproducibility of hearing protector real-ear-attenuation-at-threshold measured with three fitting methods. National Hearing Conservation Association, February 19-21, Albuquerque, NM.

Murphy WJ, Franks JR, Hall SJ, Krieg EF [1997]. Differences between binaural sound-field thresholds and monaural audiometric thresholds. J Acoust Soc Am Vol. 101, No 5, Pt. 2, 3126.


[30] US Environmental Protection Agency Workshop on Hearing Protector Devices, Washington DC, March 27 - 28, 2003 Docket OAR-2003-0024.

[31] MSHA [1999]. Dept of Labor, Mine Safety and Health Administration 30 CFR parts 56, 57 and 62, health standards for occupational noise exposure; final rule.

[32] ANSI S12.6-1984 [1984]. American National Standards Institute: Methods for Measuring the Real-Ear Attenuation of Hearing Protectors. New York: American National Standards Institute.

[33] Berger EH, Franks JR [1996]. The validity of predicting the field attenuation of hearing protectors from laboratory subject-fit data. J Acoust Soc Am Vol. 100 No 4 Pt 2, 2674.

[34] Franks JR, Murphy WJ, Simon SD [1996]. Repeatability and reproducibility in hearing protector testing. J. Acoust Soc Am Vol 99 No 3 Pt. 2, 2464.

[35] Occupational Safety and Health Administration [2001]. New developments in hearing protector labeling. In OSHA Technical Manual, chapter 5. Washington, DC: OSHA Office of Science and Technology Assessment.

[36] International Organization for Standardization [1990]. Acoustics – Hearing Protectors – Part 1: Subjective method for the measurement of sound attenuation. (ISO, Geneva). Reference No. ISO 4869-1.

[37] International Organization for Standardization [1990]. Acoustics – Hearing Protectors – Part 2: Estimation of effective A-weighted sound pressure levels when hearing protectors are worn. (International Standards Organization, Geneva). Reference No. ISO 4869-2.

[38] International Standards Organization [2005]. Acoustics – Hearing Protectors – Part 7: Subject fit method for estimation of noise reduction. Reference No. ISO/CD 4869-75 ISO TC 43/SC 1/WG 17.





About NIOSH | Site Map | Contact Us | Site developed by NIOSH HLR Program