R&D Portfolio - Research Goal 2.5:
Develop hearing protection recommendations for noise-exposed hearing-impaired workers
Of the 19 million U.S. adults estimated to have hearing impairment, nearly half are currently employed. Nine of ten coal miners, four of seven carpenters, and one of three automobile production workers with at least 20 years of employment have material hearing impairment due to noise exposure., , , , ,  Many hearing losses are incurred during the first five to ten years of employment.,  Workers frequently spend the rest of their careers trying to function in a noisy environment impaired by a hearing deficit.
Noise-exposed, hearing-impaired workers face special problems. Conventional hearing protectors typically improve speech intelligibility for normal-hearing persons; however, hearing protectors degrade speech intelligibility for hearing-impaired listeners.17, 18, , 19 Hearing protection also diminishes the ability of hearing-impaired workers to perceive certain warning signals20, 21 and monitor sounds in the work environment (e.g., equipment noises). Hearing-impaired workers have also been shown have an increased risk of occupational injuries.22
Current hearing conservation regulations do not distinguish between workers who have normal hearing and those who have hearing loss. Although the Americans with Disabilities Act of 1990 requires employers to make reasonable accommodation for handicapped workers, it provides no guidelines for managing hearing-impaired workers except those who are completely deaf. No government or professional organization has published guidelines or policies concerning the management of noise-exposed, hearing-impaired workers; therefore hearing conservation professionals do not have the information necessary to make appropriate recommendations to accommodate these individuals.
In the 1988 “Proposed National Strategy for the Prevention of Noise-Induced Hearing Loss,” NIOSH noted that “the job-related consequences of occupational NIHL may threaten a worker’s employment status.” Rehabilitation and accommodation strategies for noise-exposed, hearing-impaired workers was identified as a research need in the 1998 revision of the noise criteria document.
In 2002, the HLR program conducted a series of focus groups and in-depth interviews with noise-exposed hearing-impaired workers, supervisors of such workers, and managers of hearing conservation programs. The objective was to obtain their perspective on the effect that hearing loss and noise exposure have on safety, communication, and job performance, difficulties encountered, information needed to effectively accommodate these workers, and knowledge of currently-available options. Workers, supervisors, and hearing conservation managers reported that working in noise with a hearing loss does not have much of an effect on worker productivity, but does present a concern for employee safety, particularly regarding communication and the ability to hear important environmental sounds.
The graph demonstrates the prediction of the HLR model which combines noise exposure, HPD attenuation and hearing aid gain to estimate the exposure a worker would receive at the eardrum.
The HLR program also demonstrated that using hearing aids under earmuffs is sometimes possible without resulting in hazardous exposures, and this option can improve speech intelligibility. Acoustic mannequin measures confirmed the model’s accuracy.
An assessment/intervention protocol for hearing-impaired HPD users was developed and tested in the HLR program’s audiological laboratory. NIOSH, General Motors, and the UAW field-tested the protocol with a group of hearing-impaired, noise-exposed manufacturing employees in Michigan. The goal is to develop the simplest protocol possible that will still allow hearing conservation professionals to recommend appropriate accommodations for noise-exposed, hearing-impaired workers.
 National Center for Health Statistics . Prevalence and Characteristics of Persons With Hearing Trouble: United States, 1990-91. Vital and Health Statistics, Series 10, No. 188. DHHS Publication no. (PHS) 94-1516.
 National Institute for Occupational Safety and Health (NIOSH) . Analysis of audiograms for a large cohort of noise-exposed miners. Franks, JR , pp. 1-7, and cover letter to Davitt McAteer from Linda Rosenstock, August 6, 1996.
 National Institute for Occupational Safety and Health (NIOSH) . Prevalence of hearing loss for noise–exposed metal/nonmetal miners. Franks, JR, pp. 1-5, and cover letter to Andrea Hricko from Gregory Wagner, October 7, 1997.
 Stephenson M . New approaches for preventing hearing loss among carpenters. Abstracts of the Sixth Annual Carpenters Health and Safety Conference, Palm Springs, CA, March 24-28.
 Simpson TH, Stewart M, Blakley BW . Audiometric referral criteria for industrial hearing conservation programs. Arch Otolaryngol Head Neck Surg;121(4):407-11.
 Stephenson M, Merry C . Hearing loss among coal miners and measures to protect hearing. Holmes Safety Association Bulletin, October issue, pp. 3-5.
 Grayson L . Effective prevention of hearing loss in miners. Holmes Safety Association Bulletin, January issue, pp. 3-5.
 Rosler G . Progression of hearing loss caused by occupational noise. Scand Audiol 23(1):13-37.
 Ward WD, Royster JD, Royster LH . Auditory and nonauditory effects of noise. In: Berger EH, Royster LH, Royster JD, Driscoll DP, & Layne M (Eds), The Noise Manual Fifth Edition. Fairfax, VA: American Industrial Hygiene Association, pp123-147.
 Abel SM, Armstrong SM, Giguere C . Auditory-perception with level dependent hearing protectors. The effects of age and hearing loss. Scand Audiology, 22(2):71-85.
 NIOSH . Proposed national Strategies for the Prevention of Leading Work-Related Diseases and Injuries Part 2. Assoc Schools of Public Health. U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health.