Excessive ambient noise levels in audiometric test booths may elevate and therefore invalidate hearing thresholds of employees included in a hearing conservation program. This study was conducted to determine if a sample of mobile test vans and trailers operating in the Midwest met the 1983Occupational Safety and Health Administration (OSHA) maximum permissible ambient noise levels (MPANLs), the MPANLs in the American National Standards Institute (ANSI) S3.1-1991, and the suggested National Hearing Conservation Association (NHCA) values. Ambi
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