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Advanced hearing protector study conducted at: General Motors Metal Fabricating Division Flint Metal Center - Flint, Michigan, January 2004 - February 2005 (superseded).

Murphy WJ; Davis RR; Byrne DC; Franks JR
Cincinnati, OH: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, EPHB 312-11a, 2007 May; :1-42
This document has been superseded and the new version can be found <a href=""target="_blank">here</a>. National Institute for Occupational Safety and Health (NIOSH) investigators were requested to evaluate the use of customized hearing protection devices for comfort, acceptance, and noise reduction performance. This request came from the UAW-GM Center for Human Resources (UAW-GM CHR). The plant selected for the study was the Flint Metal Center in Flint, Michigan. With the assistance of the United Auto Workers Local 659, a total of 228 workers were recruited for a study to evaluate an advanced technology semi-custom earplug made by Sonomax Hearing Healthcare, Inc. NIOSH developed a protocol for an investigation which tested three groups of employees: 1) Group A was fit with the custom-molded earplug; 2) Group B was fit with hearing protectors already available in the plant, and was counseled on proper fitting and selection of hearing protection; and 3) Group C used protectors available in the plant but was not directly counseled regarding selection or fitting of hearing protection. NIOSH investigators made four visits to the facility in February 2004, March 2004, June 2004, and January/February 2005. Objective measurements of hearing protector performance along with the subjective evaluation of employees' beliefs, attitudes, and hearing protector comfort was assessed during each visit. Individual hearing tests were administered during the first and last visits. Ideally, an employee's protected exposure level should be between 70 and 85 dBA. Based on fit-testing results, employees tended to prefer overprotection (more attenuation than was necessary according to the GM-provided noise exposure data). This may be related to the unique impulsive noise environment of the stamping plant. The custom hearing protectors provided approximately 50-62% of the workers with an appropriate amount of noise reduction. Other protectors used in this study generally provided 30% of wearers with an ideal amount of protection. The acceptance rate of the Sonomax earplug was approximately 25% based upon the Group A dropout rate and the monthly walk-through assessments conducted during the course of the year-long investigation. Factors influencing acceptance included dislike of the feel of wet lubrication in the ear, difficulty in quickly donning hearing protection, comfort and sanitation issues. If the plant were to adopt the custom plug, generic hearing protectors must still be stocked. There are days when workers forget their custom plugs or when custom plugs are damaged and the worker must wait for a re-fit. Less than 1% (in the present study) of workers have extremely small or large ear canals and cannot be fit with current Sonomax earplugs. A major concern is employees "loaned" to different plant departments where noise levels may be significantly different from the home department. Hearing protector attenuation may have to be adjusted to accommodate different levels of noise to adequately protect the worker. We found the Sonomax earplug to be safe and effective for use in an industrial environment. The high initial cost and low worker acceptance may make it a poor choice in this application. A constant noise environment or a worker pool inexperienced in hearing protector use may make this option more attractive.
Control-technology; Engineering-controls; Ear-protection; Ear-protectors; Hearing-protection; Noise; Noise-control; Noise-protection; Industrial-factory-workers; Industrial-noise; Workplace-studies; Workers; Region-5; Automotive-industry
National Institute for Occupational Safety and Health, Division of Applied Research and Technology, Engineering and Physical Hazards Branch, Mail Stop R-5, 4676 Columbia Parkway, Cincinnati, OH45226-1998
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Field Studies; Control Technology
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NIOSH Division
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Disease and Injury: Hearing Loss
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National Institute for Occupational Safety and Health
Page last reviewed: July 1, 2022
Content source: National Institute for Occupational Safety and Health Education and Information Division